(function(f) { if (typeof exports === 'object' && typeof module !== 'undefined') { module.exports = f() } else if (typeof window.define === 'function' && window.define.amd) { window.define([], f) } else { var g; if (typeof window !== 'undefined') { g = window } else if (typeof global !== 'undefined') { g = global } else if (typeof self !== 'undefined') { g = self } else { g = this }g.adapter = f() } })(function() {
  return (function() { function r(e, n, t) { function o(i, f) { if (!n[i]) { if (!e[i]) { var c = typeof require === 'function' && require; if (!f && c) return c(i, !0); if (u) return u(i, !0); var a = new Error("Cannot find module '" + i + "'"); a.code = 'MODULE_NOT_FOUND'; throw a } var p = n[i] = { exports: {}}; e[i][0].call(p.exports, function(r) { var n = e[i][1][r]; return o(n || r) }, p, p.exports, r, e, n, t) } return n[i].exports } for (var u = typeof require === 'function' && require, i = 0; i < t.length; i++)o(t[i]); return o } return r })()({ 1: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */

    'use strict'

    var _adapter_factory = require('./adapter_factory.js')

    var adapter = (0, _adapter_factory.adapterFactory)({ window: window })
    module.exports = adapter // this is the difference from adapter_core.
  }, { './adapter_factory.js': 2 }], 2: [function(require, module, exports) {
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.adapterFactory = adapterFactory

    var _utils = require('./utils')

    var utils = _interopRequireWildcard(_utils)

    var _chrome_shim = require('./chrome/chrome_shim')

    var chromeShim = _interopRequireWildcard(_chrome_shim)

    var _edge_shim = require('./edge/edge_shim')

    var edgeShim = _interopRequireWildcard(_edge_shim)

    var _firefox_shim = require('./firefox/firefox_shim')

    var firefoxShim = _interopRequireWildcard(_firefox_shim)

    var _safari_shim = require('./safari/safari_shim')

    var safariShim = _interopRequireWildcard(_safari_shim)

    var _common_shim = require('./common_shim')

    var commonShim = _interopRequireWildcard(_common_shim)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    // Shimming starts here.
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    function adapterFactory() {
      var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {}
      var window = _ref.window

      var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
        shimChrome: true,
        shimFirefox: true,
        shimEdge: true,
        shimSafari: true
      }

      // Utils.
      var logging = utils.log
      var browserDetails = utils.detectBrowser(window)

      var adapter = {
        browserDetails: browserDetails,
        commonShim: commonShim,
        extractVersion: utils.extractVersion,
        disableLog: utils.disableLog,
        disableWarnings: utils.disableWarnings
      }

      // Shim browser if found.
      switch (browserDetails.browser) {
        case 'chrome':
          if (!chromeShim || !chromeShim.shimPeerConnection || !options.shimChrome) {
            logging('Chrome shim is not included in this adapter release.')
            return adapter
          }
          if (browserDetails.version === null) {
            logging('Chrome shim can not determine version, not shimming.')
            return adapter
          }
          logging('adapter.js shimming chrome.')
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = chromeShim

          chromeShim.shimGetUserMedia(window)
          chromeShim.shimMediaStream(window)
          chromeShim.shimPeerConnection(window)
          chromeShim.shimOnTrack(window)
          chromeShim.shimAddTrackRemoveTrack(window)
          chromeShim.shimGetSendersWithDtmf(window)
          chromeShim.shimGetStats(window)
          chromeShim.shimSenderReceiverGetStats(window)
          chromeShim.fixNegotiationNeeded(window)

          commonShim.shimRTCIceCandidate(window)
          commonShim.shimConnectionState(window)
          commonShim.shimMaxMessageSize(window)
          commonShim.shimSendThrowTypeError(window)
          commonShim.removeAllowExtmapMixed(window)
          break
        case 'firefox':
          if (!firefoxShim || !firefoxShim.shimPeerConnection || !options.shimFirefox) {
            logging('Firefox shim is not included in this adapter release.')
            return adapter
          }
          logging('adapter.js shimming firefox.')
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = firefoxShim

          firefoxShim.shimGetUserMedia(window)
          firefoxShim.shimPeerConnection(window)
          firefoxShim.shimOnTrack(window)
          firefoxShim.shimRemoveStream(window)
          firefoxShim.shimSenderGetStats(window)
          firefoxShim.shimReceiverGetStats(window)
          firefoxShim.shimRTCDataChannel(window)
          firefoxShim.shimAddTransceiver(window)
          firefoxShim.shimCreateOffer(window)
          firefoxShim.shimCreateAnswer(window)

          commonShim.shimRTCIceCandidate(window)
          commonShim.shimConnectionState(window)
          commonShim.shimMaxMessageSize(window)
          commonShim.shimSendThrowTypeError(window)
          break
        case 'edge':
          if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
            logging('MS edge shim is not included in this adapter release.')
            return adapter
          }
          logging('adapter.js shimming edge.')
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = edgeShim

          edgeShim.shimGetUserMedia(window)
          edgeShim.shimGetDisplayMedia(window)
          edgeShim.shimPeerConnection(window)
          edgeShim.shimReplaceTrack(window)

          // the edge shim implements the full RTCIceCandidate object.

          commonShim.shimMaxMessageSize(window)
          commonShim.shimSendThrowTypeError(window)
          break
        case 'safari':
          if (!safariShim || !options.shimSafari) {
            logging('Safari shim is not included in this adapter release.')
            return adapter
          }
          logging('adapter.js shimming safari.')
          // Export to the adapter global object visible in the browser.
          adapter.browserShim = safariShim

          safariShim.shimRTCIceServerUrls(window)
          safariShim.shimCreateOfferLegacy(window)
          safariShim.shimCallbacksAPI(window)
          safariShim.shimLocalStreamsAPI(window)
          safariShim.shimRemoteStreamsAPI(window)
          safariShim.shimTrackEventTransceiver(window)
          safariShim.shimGetUserMedia(window)
          safariShim.shimAudioContext(window)

          commonShim.shimRTCIceCandidate(window)
          commonShim.shimMaxMessageSize(window)
          commonShim.shimSendThrowTypeError(window)
          commonShim.removeAllowExtmapMixed(window)
          break
        default:
          logging('Unsupported browser!')
          break
      }

      return adapter
    }

  // Browser shims.
  }, { './chrome/chrome_shim': 3, './common_shim': 6, './edge/edge_shim': 7, './firefox/firefox_shim': 11, './safari/safari_shim': 14, './utils': 15 }], 3: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    var _getusermedia = require('./getusermedia')

    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia
      }
    })

    var _getdisplaymedia = require('./getdisplaymedia')

    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia
      }
    })
    exports.shimMediaStream = shimMediaStream
    exports.shimOnTrack = shimOnTrack
    exports.shimGetSendersWithDtmf = shimGetSendersWithDtmf
    exports.shimGetStats = shimGetStats
    exports.shimSenderReceiverGetStats = shimSenderReceiverGetStats
    exports.shimAddTrackRemoveTrackWithNative = shimAddTrackRemoveTrackWithNative
    exports.shimAddTrackRemoveTrack = shimAddTrackRemoveTrack
    exports.shimPeerConnection = shimPeerConnection
    exports.fixNegotiationNeeded = fixNegotiationNeeded

    var _utils = require('../utils.js')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }) } else { obj[key] = value } return obj }

    function shimMediaStream(window) {
      window.MediaStream = window.MediaStream || window.webkitMediaStream
    }

    function shimOnTrack(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('ontrack' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
          get: function get() {
            return this._ontrack
          },
          set: function set(f) {
            if (this._ontrack) {
              this.removeEventListener('track', this._ontrack)
            }
            this.addEventListener('track', this._ontrack = f)
          },

          enumerable: true,
          configurable: true
        })
        var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription
        window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
          var _this = this

          if (!this._ontrackpoly) {
            this._ontrackpoly = function(e) {
              // onaddstream does not fire when a track is added to an existing
              // stream. But stream.onaddtrack is implemented so we use that.
              e.stream.addEventListener('addtrack', function(te) {
                var receiver = void 0
                if (window.RTCPeerConnection.prototype.getReceivers) {
                  receiver = _this.getReceivers().find(function(r) {
                    return r.track && r.track.id === te.track.id
                  })
                } else {
                  receiver = { track: te.track }
                }

                var event = new Event('track')
                event.track = te.track
                event.receiver = receiver
                event.transceiver = { receiver: receiver }
                event.streams = [e.stream]
                _this.dispatchEvent(event)
              })
              e.stream.getTracks().forEach(function(track) {
                var receiver = void 0
                if (window.RTCPeerConnection.prototype.getReceivers) {
                  receiver = _this.getReceivers().find(function(r) {
                    return r.track && r.track.id === track.id
                  })
                } else {
                  receiver = { track: track }
                }
                var event = new Event('track')
                event.track = track
                event.receiver = receiver
                event.transceiver = { receiver: receiver }
                event.streams = [e.stream]
                _this.dispatchEvent(event)
              })
            }
            this.addEventListener('addstream', this._ontrackpoly)
          }
          return origSetRemoteDescription.apply(this, arguments)
        }
      } else {
        // even if RTCRtpTransceiver is in window, it is only used and
        // emitted in unified-plan. Unfortunately this means we need
        // to unconditionally wrap the event.
        utils.wrapPeerConnectionEvent(window, 'track', function(e) {
          if (!e.transceiver) {
            Object.defineProperty(e, 'transceiver', { value: { receiver: e.receiver }})
          }
          return e
        })
      }
    }

    function shimGetSendersWithDtmf(window) {
      // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('getSenders' in window.RTCPeerConnection.prototype) && 'createDTMFSender' in window.RTCPeerConnection.prototype) {
        var shimSenderWithDtmf = function shimSenderWithDtmf(pc, track) {
          return {
            track: track,
            get dtmf() {
              if (this._dtmf === undefined) {
                if (track.kind === 'audio') {
                  this._dtmf = pc.createDTMFSender(track)
                } else {
                  this._dtmf = null
                }
              }
              return this._dtmf
            },
            _pc: pc
          }
        }

        // augment addTrack when getSenders is not available.
        if (!window.RTCPeerConnection.prototype.getSenders) {
          window.RTCPeerConnection.prototype.getSenders = function getSenders() {
            this._senders = this._senders || []
            return this._senders.slice() // return a copy of the internal state.
          }
          var origAddTrack = window.RTCPeerConnection.prototype.addTrack
          window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
            var sender = origAddTrack.apply(this, arguments)
            if (!sender) {
              sender = shimSenderWithDtmf(this, track)
              this._senders.push(sender)
            }
            return sender
          }

          var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack
          window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
            origRemoveTrack.apply(this, arguments)
            var idx = this._senders.indexOf(sender)
            if (idx !== -1) {
              this._senders.splice(idx, 1)
            }
          }
        }
        var origAddStream = window.RTCPeerConnection.prototype.addStream
        window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
          var _this2 = this

          this._senders = this._senders || []
          origAddStream.apply(this, [stream])
          stream.getTracks().forEach(function(track) {
            _this2._senders.push(shimSenderWithDtmf(_this2, track))
          })
        }

        var origRemoveStream = window.RTCPeerConnection.prototype.removeStream
        window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
          var _this3 = this

          this._senders = this._senders || []
          origRemoveStream.apply(this, [stream])

          stream.getTracks().forEach(function(track) {
            var sender = _this3._senders.find(function(s) {
              return s.track === track
            })
            if (sender) {
              // remove sender
              _this3._senders.splice(_this3._senders.indexOf(sender), 1)
            }
          })
        }
      } else if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && 'getSenders' in window.RTCPeerConnection.prototype && 'createDTMFSender' in window.RTCPeerConnection.prototype && window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
        var origGetSenders = window.RTCPeerConnection.prototype.getSenders
        window.RTCPeerConnection.prototype.getSenders = function getSenders() {
          var _this4 = this

          var senders = origGetSenders.apply(this, [])
          senders.forEach(function(sender) {
            sender._pc = _this4
            return sender._pc
          })
          return senders
        }

        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
          get: function get() {
            if (this._dtmf === undefined) {
              if (this.track.kind === 'audio') {
                this._dtmf = this._pc.createDTMFSender(this.track)
              } else {
                this._dtmf = null
              }
            }
            return this._dtmf
          }
        })
      }
    }

    function shimGetStats(window) {
      if (!window.RTCPeerConnection) {
        return
      }

      var origGetStats = window.RTCPeerConnection.prototype.getStats
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        var _this5 = this

        var _arguments = Array.prototype.slice.call(arguments)
        var selector = _arguments[0]
        var onSucc = _arguments[1]
        var onErr = _arguments[2]

        // If selector is a function then we are in the old style stats so just
        // pass back the original getStats format to avoid breaking old users.

        if (arguments.length > 0 && typeof selector === 'function') {
          return origGetStats.apply(this, arguments)
        }

        // When spec-style getStats is supported, return those when called with
        // either no arguments or the selector argument is null.
        if (origGetStats.length === 0 && (arguments.length === 0 || typeof selector !== 'function')) {
          return origGetStats.apply(this, [])
        }

        var fixChromeStats_ = function fixChromeStats_(response) {
          var standardReport = {}
          var reports = response.result()
          reports.forEach(function(report) {
            var standardStats = {
              id: report.id,
              timestamp: report.timestamp,
              type: {
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
              }[report.type] || report.type
            }
            report.names().forEach(function(name) {
              standardStats[name] = report.stat(name)
            })
            standardReport[standardStats.id] = standardStats
          })

          return standardReport
        }

        // shim getStats with maplike support
        var makeMapStats = function makeMapStats(stats) {
          return new Map(Object.keys(stats).map(function(key) {
            return [key, stats[key]]
          }))
        }

        if (arguments.length >= 2) {
          var successCallbackWrapper_ = function successCallbackWrapper_(response) {
            onSucc(makeMapStats(fixChromeStats_(response)))
          }

          return origGetStats.apply(this, [successCallbackWrapper_, selector])
        }

        // promise-support
        return new Promise(function(resolve, reject) {
          origGetStats.apply(_this5, [function(response) {
            resolve(makeMapStats(fixChromeStats_(response)))
          }, reject])
        }).then(onSucc, onErr)
      }
    }

    function shimSenderReceiverGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender && window.RTCRtpReceiver)) {
        return
      }

      // shim sender stats.
      if (!('getStats' in window.RTCRtpSender.prototype)) {
        var origGetSenders = window.RTCPeerConnection.prototype.getSenders
        if (origGetSenders) {
          window.RTCPeerConnection.prototype.getSenders = function getSenders() {
            var _this6 = this

            var senders = origGetSenders.apply(this, [])
            senders.forEach(function(sender) {
              sender._pc = _this6
              return sender._pc
            })
            return senders
          }
        }

        var origAddTrack = window.RTCPeerConnection.prototype.addTrack
        if (origAddTrack) {
          window.RTCPeerConnection.prototype.addTrack = function addTrack() {
            var sender = origAddTrack.apply(this, arguments)
            sender._pc = this
            return sender
          }
        }
        window.RTCRtpSender.prototype.getStats = function getStats() {
          var sender = this
          return this._pc.getStats().then(function(result) {
            return (
            /* Note: this will include stats of all senders that
           *   send a track with the same id as sender.track as
           *   it is not possible to identify the RTCRtpSender.
           */
              utils.filterStats(result, sender.track, true)
            )
          })
        }
      }

      // shim receiver stats.
      if (!('getStats' in window.RTCRtpReceiver.prototype)) {
        var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers
        if (origGetReceivers) {
          window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
            var _this7 = this

            var receivers = origGetReceivers.apply(this, [])
            receivers.forEach(function(receiver) {
              receiver._pc = _this7
              return receiver._pc
            })
            return receivers
          }
        }
        utils.wrapPeerConnectionEvent(window, 'track', function(e) {
          e.receiver._pc = e.srcElement
          return e
        })
        window.RTCRtpReceiver.prototype.getStats = function getStats() {
          var receiver = this
          return this._pc.getStats().then(function(result) {
            return utils.filterStats(result, receiver.track, false)
          })
        }
      }

      if (!('getStats' in window.RTCRtpSender.prototype && 'getStats' in window.RTCRtpReceiver.prototype)) {
        return
      }

      // shim RTCPeerConnection.getStats(track).
      var origGetStats = window.RTCPeerConnection.prototype.getStats
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        if (arguments.length > 0 && arguments[0] instanceof window.MediaStreamTrack) {
          var track = arguments[0]
          var sender = void 0
          var receiver = void 0
          var err = void 0
          this.getSenders().forEach(function(s) {
            if (s.track === track) {
              if (sender) {
                err = true
              } else {
                sender = s
              }
            }
          })
          this.getReceivers().forEach(function(r) {
            if (r.track === track) {
              if (receiver) {
                err = true
              } else {
                receiver = r
              }
            }
            return r.track === track
          })
          if (err || sender && receiver) {
            return Promise.reject(new DOMException('There are more than one sender or receiver for the track.', 'InvalidAccessError'))
          } else if (sender) {
            return sender.getStats()
          } else if (receiver) {
            return receiver.getStats()
          }
          return Promise.reject(new DOMException('There is no sender or receiver for the track.', 'InvalidAccessError'))
        }
        return origGetStats.apply(this, arguments)
      }
    }

    function shimAddTrackRemoveTrackWithNative(window) {
      // shim addTrack/removeTrack with native variants in order to make
      // the interactions with legacy getLocalStreams behave as in other browsers.
      // Keeps a mapping stream.id => [stream, rtpsenders...]
      window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
        var _this8 = this

        this._shimmedLocalStreams = this._shimmedLocalStreams || {}
        return Object.keys(this._shimmedLocalStreams).map(function(streamId) {
          return _this8._shimmedLocalStreams[streamId][0]
        })
      }

      var origAddTrack = window.RTCPeerConnection.prototype.addTrack
      window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
        if (!stream) {
          return origAddTrack.apply(this, arguments)
        }
        this._shimmedLocalStreams = this._shimmedLocalStreams || {}

        var sender = origAddTrack.apply(this, arguments)
        if (!this._shimmedLocalStreams[stream.id]) {
          this._shimmedLocalStreams[stream.id] = [stream, sender]
        } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
          this._shimmedLocalStreams[stream.id].push(sender)
        }
        return sender
      }

      var origAddStream = window.RTCPeerConnection.prototype.addStream
      window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
        var _this9 = this

        this._shimmedLocalStreams = this._shimmedLocalStreams || {}

        stream.getTracks().forEach(function(track) {
          var alreadyExists = _this9.getSenders().find(function(s) {
            return s.track === track
          })
          if (alreadyExists) {
            throw new DOMException('Track already exists.', 'InvalidAccessError')
          }
        })
        var existingSenders = this.getSenders()
        origAddStream.apply(this, arguments)
        var newSenders = this.getSenders().filter(function(newSender) {
          return existingSenders.indexOf(newSender) === -1
        })
        this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders)
      }

      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        this._shimmedLocalStreams = this._shimmedLocalStreams || {}
        delete this._shimmedLocalStreams[stream.id]
        return origRemoveStream.apply(this, arguments)
      }

      var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack
      window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
        var _this10 = this

        this._shimmedLocalStreams = this._shimmedLocalStreams || {}
        if (sender) {
          Object.keys(this._shimmedLocalStreams).forEach(function(streamId) {
            var idx = _this10._shimmedLocalStreams[streamId].indexOf(sender)
            if (idx !== -1) {
              _this10._shimmedLocalStreams[streamId].splice(idx, 1)
            }
            if (_this10._shimmedLocalStreams[streamId].length === 1) {
              delete _this10._shimmedLocalStreams[streamId]
            }
          })
        }
        return origRemoveTrack.apply(this, arguments)
      }
    }

    function shimAddTrackRemoveTrack(window) {
      if (!window.RTCPeerConnection) {
        return
      }
      var browserDetails = utils.detectBrowser(window)
      // shim addTrack and removeTrack.
      if (window.RTCPeerConnection.prototype.addTrack && browserDetails.version >= 65) {
        return shimAddTrackRemoveTrackWithNative(window)
      }

      // also shim pc.getLocalStreams when addTrack is shimmed
      // to return the original streams.
      var origGetLocalStreams = window.RTCPeerConnection.prototype.getLocalStreams
      window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
        var _this11 = this

        var nativeStreams = origGetLocalStreams.apply(this)
        this._reverseStreams = this._reverseStreams || {}
        return nativeStreams.map(function(stream) {
          return _this11._reverseStreams[stream.id]
        })
      }

      var origAddStream = window.RTCPeerConnection.prototype.addStream
      window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
        var _this12 = this

        this._streams = this._streams || {}
        this._reverseStreams = this._reverseStreams || {}

        stream.getTracks().forEach(function(track) {
          var alreadyExists = _this12.getSenders().find(function(s) {
            return s.track === track
          })
          if (alreadyExists) {
            throw new DOMException('Track already exists.', 'InvalidAccessError')
          }
        })
        // Add identity mapping for consistency with addTrack.
        // Unless this is being used with a stream from addTrack.
        if (!this._reverseStreams[stream.id]) {
          var newStream = new window.MediaStream(stream.getTracks())
          this._streams[stream.id] = newStream
          this._reverseStreams[newStream.id] = stream
          stream = newStream
        }
        origAddStream.apply(this, [stream])
      }

      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        this._streams = this._streams || {}
        this._reverseStreams = this._reverseStreams || {}

        origRemoveStream.apply(this, [this._streams[stream.id] || stream])
        delete this._reverseStreams[this._streams[stream.id] ? this._streams[stream.id].id : stream.id]
        delete this._streams[stream.id]
      }

      window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
        var _this13 = this

        if (this.signalingState === 'closed') {
          throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError')
        }
        var streams = [].slice.call(arguments, 1)
        if (streams.length !== 1 || !streams[0].getTracks().find(function(t) {
          return t === track
        })) {
          // this is not fully correct but all we can manage without
          // [[associated MediaStreams]] internal slot.
          throw new DOMException('The adapter.js addTrack polyfill only supports a single ' + ' stream which is associated with the specified track.', 'NotSupportedError')
        }

        var alreadyExists = this.getSenders().find(function(s) {
          return s.track === track
        })
        if (alreadyExists) {
          throw new DOMException('Track already exists.', 'InvalidAccessError')
        }

        this._streams = this._streams || {}
        this._reverseStreams = this._reverseStreams || {}
        var oldStream = this._streams[stream.id]
        if (oldStream) {
          // this is using odd Chrome behaviour, use with caution:
          // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
          // Note: we rely on the high-level addTrack/dtmf shim to
          // create the sender with a dtmf sender.
          oldStream.addTrack(track)

          // Trigger ONN async.
          Promise.resolve().then(function() {
            _this13.dispatchEvent(new Event('negotiationneeded'))
          })
        } else {
          var newStream = new window.MediaStream([track])
          this._streams[stream.id] = newStream
          this._reverseStreams[newStream.id] = stream
          this.addStream(newStream)
        }
        return this.getSenders().find(function(s) {
          return s.track === track
        })
      }

      // replace the internal stream id with the external one and
      // vice versa.
      function replaceInternalStreamId(pc, description) {
        var sdp = description.sdp
        Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
          var externalStream = pc._reverseStreams[internalId]
          var internalStream = pc._streams[externalStream.id]
          sdp = sdp.replace(new RegExp(internalStream.id, 'g'), externalStream.id)
        })
        return new RTCSessionDescription({
          type: description.type,
          sdp: sdp
        })
      }
      function replaceExternalStreamId(pc, description) {
        var sdp = description.sdp
        Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
          var externalStream = pc._reverseStreams[internalId]
          var internalStream = pc._streams[externalStream.id]
          sdp = sdp.replace(new RegExp(externalStream.id, 'g'), internalStream.id)
        })
        return new RTCSessionDescription({
          type: description.type,
          sdp: sdp
        })
      }
      ['createOffer', 'createAnswer'].forEach(function(method) {
        var nativeMethod = window.RTCPeerConnection.prototype[method]
        var methodObj = _defineProperty({}, method, function() {
          var _this14 = this

          var args = arguments
          var isLegacyCall = arguments.length && typeof arguments[0] === 'function'
          if (isLegacyCall) {
            return nativeMethod.apply(this, [function(description) {
              var desc = replaceInternalStreamId(_this14, description)
              args[0].apply(null, [desc])
            }, function(err) {
              if (args[1]) {
                args[1].apply(null, err)
              }
            }, arguments[2]])
          }
          return nativeMethod.apply(this, arguments).then(function(description) {
            return replaceInternalStreamId(_this14, description)
          })
        })
        window.RTCPeerConnection.prototype[method] = methodObj[method]
      })

      var origSetLocalDescription = window.RTCPeerConnection.prototype.setLocalDescription
      window.RTCPeerConnection.prototype.setLocalDescription = function setLocalDescription() {
        if (!arguments.length || !arguments[0].type) {
          return origSetLocalDescription.apply(this, arguments)
        }
        arguments[0] = replaceExternalStreamId(this, arguments[0])
        return origSetLocalDescription.apply(this, arguments)
      }

      // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier

      var origLocalDescription = Object.getOwnPropertyDescriptor(window.RTCPeerConnection.prototype, 'localDescription')
      Object.defineProperty(window.RTCPeerConnection.prototype, 'localDescription', {
        get: function get() {
          var description = origLocalDescription.get.apply(this)
          if (description.type === '') {
            return description
          }
          return replaceInternalStreamId(this, description)
        }
      })

      window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
        var _this15 = this

        if (this.signalingState === 'closed') {
          throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError')
        }
        // We can not yet check for sender instanceof RTCRtpSender
        // since we shim RTPSender. So we check if sender._pc is set.
        if (!sender._pc) {
          throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' + 'does not implement interface RTCRtpSender.', 'TypeError')
        }
        var isLocal = sender._pc === this
        if (!isLocal) {
          throw new DOMException('Sender was not created by this connection.', 'InvalidAccessError')
        }

        // Search for the native stream the senders track belongs to.
        this._streams = this._streams || {}
        var stream = void 0
        Object.keys(this._streams).forEach(function(streamid) {
          var hasTrack = _this15._streams[streamid].getTracks().find(function(track) {
            return sender.track === track
          })
          if (hasTrack) {
            stream = _this15._streams[streamid]
          }
        })

        if (stream) {
          if (stream.getTracks().length === 1) {
            // if this is the last track of the stream, remove the stream. This
            // takes care of any shimmed _senders.
            this.removeStream(this._reverseStreams[stream.id])
          } else {
            // relying on the same odd chrome behaviour as above.
            stream.removeTrack(sender.track)
          }
          this.dispatchEvent(new Event('negotiationneeded'))
        }
      }
    }

    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window)

      if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
        // very basic support for old versions.
        window.RTCPeerConnection = window.webkitRTCPeerConnection
      }
      if (!window.RTCPeerConnection) {
        return
      }

      var addIceCandidateNullSupported = window.RTCPeerConnection.prototype.addIceCandidate.length === 0

      // shim implicit creation of RTCSessionDescription/RTCIceCandidate
      if (browserDetails.version < 53) {
        ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function(method) {
          var nativeMethod = window.RTCPeerConnection.prototype[method]
          var methodObj = _defineProperty({}, method, function() {
            arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0])
            return nativeMethod.apply(this, arguments)
          })
          window.RTCPeerConnection.prototype[method] = methodObj[method]
        })
      }

      // support for addIceCandidate(null or undefined)
      var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate
      window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
        if (!addIceCandidateNullSupported && !arguments[0]) {
          if (arguments[1]) {
            arguments[1].apply(null)
          }
          return Promise.resolve()
        }
        // Firefox 68+ emits and processes {candidate: "", ...}, ignore
        // in older versions. Native support planned for Chrome M77.
        if (browserDetails.version < 78 && arguments[0] && arguments[0].candidate === '') {
          return Promise.resolve()
        }
        return nativeAddIceCandidate.apply(this, arguments)
      }
    }

    function fixNegotiationNeeded(window) {
      utils.wrapPeerConnectionEvent(window, 'negotiationneeded', function(e) {
        var pc = e.target
        if (pc.signalingState !== 'stable') {
          return
        }
        return e
      })
    }
  }, { '../utils.js': 15, './getdisplaymedia': 4, './getusermedia': 5 }], 4: [function(require, module, exports) {
    /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = shimGetDisplayMedia
    function shimGetDisplayMedia(window, getSourceId) {
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return
      }
      if (!window.navigator.mediaDevices) {
        return
      }
      // getSourceId is a function that returns a promise resolving with
      // the sourceId of the screen/window/tab to be shared.
      if (typeof getSourceId !== 'function') {
        console.error('shimGetDisplayMedia: getSourceId argument is not ' + 'a function')
        return
      }
      window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
        return getSourceId(constraints).then(function(sourceId) {
          var widthSpecified = constraints.video && constraints.video.width
          var heightSpecified = constraints.video && constraints.video.height
          var frameRateSpecified = constraints.video && constraints.video.frameRate
          constraints.video = {
            mandatory: {
              chromeMediaSource: 'desktop',
              chromeMediaSourceId: sourceId,
              maxFrameRate: frameRateSpecified || 3
            }
          }
          if (widthSpecified) {
            constraints.video.mandatory.maxWidth = widthSpecified
          }
          if (heightSpecified) {
            constraints.video.mandatory.maxHeight = heightSpecified
          }
          return window.navigator.mediaDevices.getUserMedia(constraints)
        })
      }
    }
  }, {}], 5: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    exports.shimGetUserMedia = shimGetUserMedia

    var _utils = require('../utils.js')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    var logging = utils.log

    function shimGetUserMedia(window) {
      var navigator = window && window.navigator

      if (!navigator.mediaDevices) {
        return
      }

      var browserDetails = utils.detectBrowser(window)

      var constraintsToChrome_ = function constraintsToChrome_(c) {
        if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) !== 'object' || c.mandatory || c.optional) {
          return c
        }
        var cc = {}
        Object.keys(c).forEach(function(key) {
          if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
            return
          }
          var r = _typeof(c[key]) === 'object' ? c[key] : { ideal: c[key] }
          if (r.exact !== undefined && typeof r.exact === 'number') {
            r.min = r.max = r.exact
          }
          var oldname_ = function oldname_(prefix, name) {
            if (prefix) {
              return prefix + name.charAt(0).toUpperCase() + name.slice(1)
            }
            return name === 'deviceId' ? 'sourceId' : name
          }
          if (r.ideal !== undefined) {
            cc.optional = cc.optional || []
            var oc = {}
            if (typeof r.ideal === 'number') {
              oc[oldname_('min', key)] = r.ideal
              cc.optional.push(oc)
              oc = {}
              oc[oldname_('max', key)] = r.ideal
              cc.optional.push(oc)
            } else {
              oc[oldname_('', key)] = r.ideal
              cc.optional.push(oc)
            }
          }
          if (r.exact !== undefined && typeof r.exact !== 'number') {
            cc.mandatory = cc.mandatory || {}
            cc.mandatory[oldname_('', key)] = r.exact
          } else {
            ['min', 'max'].forEach(function(mix) {
              if (r[mix] !== undefined) {
                cc.mandatory = cc.mandatory || {}
                cc.mandatory[oldname_(mix, key)] = r[mix]
              }
            })
          }
        })
        if (c.advanced) {
          cc.optional = (cc.optional || []).concat(c.advanced)
        }
        return cc
      }

      var shimConstraints_ = function shimConstraints_(constraints, func) {
        if (browserDetails.version >= 61) {
          return func(constraints)
        }
        constraints = JSON.parse(JSON.stringify(constraints))
        if (constraints && _typeof(constraints.audio) === 'object') {
          var remap = function remap(obj, a, b) {
            if (a in obj && !(b in obj)) {
              obj[b] = obj[a]
              delete obj[a]
            }
          }
          constraints = JSON.parse(JSON.stringify(constraints))
          remap(constraints.audio, 'autoGainControl', 'googAutoGainControl')
          remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression')
          constraints.audio = constraintsToChrome_(constraints.audio)
        }
        if (constraints && _typeof(constraints.video) === 'object') {
          // Shim facingMode for mobile & surface pro.
          var face = constraints.video.facingMode
          face = face && ((typeof face === 'undefined' ? 'undefined' : _typeof(face)) === 'object' ? face : { ideal: face })
          var getSupportedFacingModeLies = browserDetails.version < 66

          if (face && (face.exact === 'user' || face.exact === 'environment' || face.ideal === 'user' || face.ideal === 'environment') && !(navigator.mediaDevices.getSupportedConstraints && navigator.mediaDevices.getSupportedConstraints().facingMode && !getSupportedFacingModeLies)) {
            delete constraints.video.facingMode
            var matches = void 0
            if (face.exact === 'environment' || face.ideal === 'environment') {
              matches = ['back', 'rear']
            } else if (face.exact === 'user' || face.ideal === 'user') {
              matches = ['front']
            }
            if (matches) {
              // Look for matches in label, or use last cam for back (typical).
              return navigator.mediaDevices.enumerateDevices().then(function(devices) {
                devices = devices.filter(function(d) {
                  return d.kind === 'videoinput'
                })
                var dev = devices.find(function(d) {
                  return matches.some(function(match) {
                    return d.label.toLowerCase().includes(match)
                  })
                })
                if (!dev && devices.length && matches.includes('back')) {
                  dev = devices[devices.length - 1] // more likely the back cam
                }
                if (dev) {
                  constraints.video.deviceId = face.exact ? { exact: dev.deviceId } : { ideal: dev.deviceId }
                }
                constraints.video = constraintsToChrome_(constraints.video)
                logging('chrome: ' + JSON.stringify(constraints))
                return func(constraints)
              })
            }
          }
          constraints.video = constraintsToChrome_(constraints.video)
        }
        logging('chrome: ' + JSON.stringify(constraints))
        return func(constraints)
      }

      var shimError_ = function shimError_(e) {
        if (browserDetails.version >= 64) {
          return e
        }
        return {
          name: {
            PermissionDeniedError: 'NotAllowedError',
            PermissionDismissedError: 'NotAllowedError',
            InvalidStateError: 'NotAllowedError',
            DevicesNotFoundError: 'NotFoundError',
            ConstraintNotSatisfiedError: 'OverconstrainedError',
            TrackStartError: 'NotReadableError',
            MediaDeviceFailedDueToShutdown: 'NotAllowedError',
            MediaDeviceKillSwitchOn: 'NotAllowedError',
            TabCaptureError: 'AbortError',
            ScreenCaptureError: 'AbortError',
            DeviceCaptureError: 'AbortError'
          }[e.name] || e.name,
          message: e.message,
          constraint: e.constraint || e.constraintName,
          toString: function toString() {
            return this.name + (this.message && ': ') + this.message
          }
        }
      }

      var getUserMedia_ = function getUserMedia_(constraints, onSuccess, onError) {
        shimConstraints_(constraints, function(c) {
          navigator.webkitGetUserMedia(c, onSuccess, function(e) {
            if (onError) {
              onError(shimError_(e))
            }
          })
        })
      }
      navigator.getUserMedia = getUserMedia_.bind(navigator)

      // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
      // function which returns a Promise, it does not accept spec-style
      // constraints.
      if (navigator.mediaDevices.getUserMedia) {
        var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices)
        navigator.mediaDevices.getUserMedia = function(cs) {
          return shimConstraints_(cs, function(c) {
            return origGetUserMedia(c).then(function(stream) {
              if (c.audio && !stream.getAudioTracks().length || c.video && !stream.getVideoTracks().length) {
                stream.getTracks().forEach(function(track) {
                  track.stop()
                })
                throw new DOMException('', 'NotFoundError')
              }
              return stream
            }, function(e) {
              return Promise.reject(shimError_(e))
            })
          })
        }
      }
    }
  }, { '../utils.js': 15 }], 6: [function(require, module, exports) {
    /*
 *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    exports.shimRTCIceCandidate = shimRTCIceCandidate
    exports.shimMaxMessageSize = shimMaxMessageSize
    exports.shimSendThrowTypeError = shimSendThrowTypeError
    exports.shimConnectionState = shimConnectionState
    exports.removeAllowExtmapMixed = removeAllowExtmapMixed

    var _sdp = require('sdp')

    var _sdp2 = _interopRequireDefault(_sdp)

    var _utils = require('./utils')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj } }

    function shimRTCIceCandidate(window) {
      // foundation is arbitrarily chosen as an indicator for full support for
      // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
      if (!window.RTCIceCandidate || window.RTCIceCandidate && 'foundation' in window.RTCIceCandidate.prototype) {
        return
      }

      var NativeRTCIceCandidate = window.RTCIceCandidate
      window.RTCIceCandidate = function RTCIceCandidate(args) {
        // Remove the a= which shouldn't be part of the candidate string.
        if ((typeof args === 'undefined' ? 'undefined' : _typeof(args)) === 'object' && args.candidate && args.candidate.indexOf('a=') === 0) {
          args = JSON.parse(JSON.stringify(args))
          args.candidate = args.candidate.substr(2)
        }

        if (args.candidate && args.candidate.length) {
          // Augment the native candidate with the parsed fields.
          var nativeCandidate = new NativeRTCIceCandidate(args)
          var parsedCandidate = _sdp2.default.parseCandidate(args.candidate)
          var augmentedCandidate = Object.assign(nativeCandidate, parsedCandidate)

          // Add a serializer that does not serialize the extra attributes.
          augmentedCandidate.toJSON = function toJSON() {
            return {
              candidate: augmentedCandidate.candidate,
              sdpMid: augmentedCandidate.sdpMid,
              sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
              usernameFragment: augmentedCandidate.usernameFragment
            }
          }
          return augmentedCandidate
        }
        return new NativeRTCIceCandidate(args)
      }
      window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype

      // Hook up the augmented candidate in onicecandidate and
      // addEventListener('icecandidate', ...)
      utils.wrapPeerConnectionEvent(window, 'icecandidate', function(e) {
        if (e.candidate) {
          Object.defineProperty(e, 'candidate', {
            value: new window.RTCIceCandidate(e.candidate),
            writable: 'false'
          })
        }
        return e
      })
    }

    function shimMaxMessageSize(window) {
      if (!window.RTCPeerConnection) {
        return
      }
      var browserDetails = utils.detectBrowser(window)

      if (!('sctp' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
          get: function get() {
            return typeof this._sctp === 'undefined' ? null : this._sctp
          }
        })
      }

      var sctpInDescription = function sctpInDescription(description) {
        if (!description || !description.sdp) {
          return false
        }
        var sections = _sdp2.default.splitSections(description.sdp)
        sections.shift()
        return sections.some(function(mediaSection) {
          var mLine = _sdp2.default.parseMLine(mediaSection)
          return mLine && mLine.kind === 'application' && mLine.protocol.indexOf('SCTP') !== -1
        })
      }

      var getRemoteFirefoxVersion = function getRemoteFirefoxVersion(description) {
        // TODO: Is there a better solution for detecting Firefox?
        var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/)
        if (match === null || match.length < 2) {
          return -1
        }
        var version = parseInt(match[1], 10)
        return version
      }

      var getCanSendMaxMessageSize = function getCanSendMaxMessageSize(remoteIsFirefox) {
        // Every implementation we know can send at least 64 KiB.
        // Note: Although Chrome is technically able to send up to 256 KiB, the
        //       data does not reach the other peer reliably.
        //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
        var canSendMaxMessageSize = 65536
        if (browserDetails.browser === 'firefox') {
          if (browserDetails.version < 57) {
            if (remoteIsFirefox === -1) {
              // FF < 57 will send in 16 KiB chunks using the deprecated PPID
              // fragmentation.
              canSendMaxMessageSize = 16384
            } else {
              // However, other FF (and RAWRTC) can reassemble PPID-fragmented
              // messages. Thus, supporting ~2 GiB when sending.
              canSendMaxMessageSize = 2147483637
            }
          } else if (browserDetails.version < 60) {
            // Currently, all FF >= 57 will reset the remote maximum message size
            // to the default value when a data channel is created at a later
            // stage. :(
            // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
            canSendMaxMessageSize = browserDetails.version === 57 ? 65535 : 65536
          } else {
            // FF >= 60 supports sending ~2 GiB
            canSendMaxMessageSize = 2147483637
          }
        }
        return canSendMaxMessageSize
      }

      var getMaxMessageSize = function getMaxMessageSize(description, remoteIsFirefox) {
        // Note: 65536 bytes is the default value from the SDP spec. Also,
        //       every implementation we know supports receiving 65536 bytes.
        var maxMessageSize = 65536

        // FF 57 has a slightly incorrect default remote max message size, so
        // we need to adjust it here to avoid a failure when sending.
        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
        if (browserDetails.browser === 'firefox' && browserDetails.version === 57) {
          maxMessageSize = 65535
        }

        var match = _sdp2.default.matchPrefix(description.sdp, 'a=max-message-size:')
        if (match.length > 0) {
          maxMessageSize = parseInt(match[0].substr(19), 10)
        } else if (browserDetails.browser === 'firefox' && remoteIsFirefox !== -1) {
          // If the maximum message size is not present in the remote SDP and
          // both local and remote are Firefox, the remote peer can receive
          // ~2 GiB.
          maxMessageSize = 2147483637
        }
        return maxMessageSize
      }

      var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription
      window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
        this._sctp = null
        // Chrome decided to not expose .sctp in plan-b mode.
        // As usual, adapter.js has to do an 'ugly worakaround'
        // to cover up the mess.
        if (browserDetails.browser === 'chrome' && browserDetails.version >= 76) {
          var _getConfiguration = this.getConfiguration()
          var sdpSemantics = _getConfiguration.sdpSemantics

          if (sdpSemantics === 'plan-b') {
            Object.defineProperty(this, 'sctp', {
              get: function get() {
                return typeof this._sctp === 'undefined' ? null : this._sctp
              },

              enumerable: true,
              configurable: true
            })
          }
        }

        if (sctpInDescription(arguments[0])) {
          // Check if the remote is FF.
          var isFirefox = getRemoteFirefoxVersion(arguments[0])

          // Get the maximum message size the local peer is capable of sending
          var canSendMMS = getCanSendMaxMessageSize(isFirefox)

          // Get the maximum message size of the remote peer.
          var remoteMMS = getMaxMessageSize(arguments[0], isFirefox)

          // Determine final maximum message size
          var maxMessageSize = void 0
          if (canSendMMS === 0 && remoteMMS === 0) {
            maxMessageSize = Number.POSITIVE_INFINITY
          } else if (canSendMMS === 0 || remoteMMS === 0) {
            maxMessageSize = Math.max(canSendMMS, remoteMMS)
          } else {
            maxMessageSize = Math.min(canSendMMS, remoteMMS)
          }

          // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
          // attribute.
          var sctp = {}
          Object.defineProperty(sctp, 'maxMessageSize', {
            get: function get() {
              return maxMessageSize
            }
          })
          this._sctp = sctp
        }

        return origSetRemoteDescription.apply(this, arguments)
      }
    }

    function shimSendThrowTypeError(window) {
      if (!(window.RTCPeerConnection && 'createDataChannel' in window.RTCPeerConnection.prototype)) {
        return
      }

      // Note: Although Firefox >= 57 has a native implementation, the maximum
      //       message size can be reset for all data channels at a later stage.
      //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831

      function wrapDcSend(dc, pc) {
        var origDataChannelSend = dc.send
        dc.send = function send() {
          var data = arguments[0]
          var length = data.length || data.size || data.byteLength
          if (dc.readyState === 'open' && pc.sctp && length > pc.sctp.maxMessageSize) {
            throw new TypeError('Message too large (can send a maximum of ' + pc.sctp.maxMessageSize + ' bytes)')
          }
          return origDataChannelSend.apply(dc, arguments)
        }
      }
      var origCreateDataChannel = window.RTCPeerConnection.prototype.createDataChannel
      window.RTCPeerConnection.prototype.createDataChannel = function createDataChannel() {
        var dataChannel = origCreateDataChannel.apply(this, arguments)
        wrapDcSend(dataChannel, this)
        return dataChannel
      }
      utils.wrapPeerConnectionEvent(window, 'datachannel', function(e) {
        wrapDcSend(e.channel, e.target)
        return e
      })
    }

    /* shims RTCConnectionState by pretending it is the same as iceConnectionState.
 * See https://bugs.chromium.org/p/webrtc/issues/detail?id=6145#c12
 * for why this is a valid hack in Chrome. In Firefox it is slightly incorrect
 * since DTLS failures would be hidden. See
 * https://bugzilla.mozilla.org/show_bug.cgi?id=1265827
 * for the Firefox tracking bug.
 */
    function shimConnectionState(window) {
      if (!window.RTCPeerConnection || 'connectionState' in window.RTCPeerConnection.prototype) {
        return
      }
      var proto = window.RTCPeerConnection.prototype
      Object.defineProperty(proto, 'connectionState', {
        get: function get() {
          return {
            completed: 'connected',
            checking: 'connecting'
          }[this.iceConnectionState] || this.iceConnectionState
        },

        enumerable: true,
        configurable: true
      })
      Object.defineProperty(proto, 'onconnectionstatechange', {
        get: function get() {
          return this._onconnectionstatechange || null
        },
        set: function set(cb) {
          if (this._onconnectionstatechange) {
            this.removeEventListener('connectionstatechange', this._onconnectionstatechange)
            delete this._onconnectionstatechange
          }
          if (cb) {
            this.addEventListener('connectionstatechange', this._onconnectionstatechange = cb)
          }
        },

        enumerable: true,
        configurable: true
      });

      ['setLocalDescription', 'setRemoteDescription'].forEach(function(method) {
        var origMethod = proto[method]
        proto[method] = function() {
          if (!this._connectionstatechangepoly) {
            this._connectionstatechangepoly = function(e) {
              var pc = e.target
              if (pc._lastConnectionState !== pc.connectionState) {
                pc._lastConnectionState = pc.connectionState
                var newEvent = new Event('connectionstatechange', e)
                pc.dispatchEvent(newEvent)
              }
              return e
            }
            this.addEventListener('iceconnectionstatechange', this._connectionstatechangepoly)
          }
          return origMethod.apply(this, arguments)
        }
      })
    }

    function removeAllowExtmapMixed(window) {
      /* remove a=extmap-allow-mixed for Chrome < M71 */
      if (!window.RTCPeerConnection) {
        return
      }
      var browserDetails = utils.detectBrowser(window)
      if (browserDetails.browser === 'chrome' && browserDetails.version >= 71) {
        return
      }
      var nativeSRD = window.RTCPeerConnection.prototype.setRemoteDescription
      window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription(desc) {
        if (desc && desc.sdp && desc.sdp.indexOf('\na=extmap-allow-mixed') !== -1) {
          desc.sdp = desc.sdp.split('\n').filter(function(line) {
            return line.trim() !== 'a=extmap-allow-mixed'
          }).join('\n')
        }
        return nativeSRD.apply(this, arguments)
      }
    }
  }, { './utils': 15, 'sdp': 17 }], 7: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined

    var _getusermedia = require('./getusermedia')

    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia
      }
    })

    var _getdisplaymedia = require('./getdisplaymedia')

    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia
      }
    })
    exports.shimPeerConnection = shimPeerConnection
    exports.shimReplaceTrack = shimReplaceTrack

    var _utils = require('../utils')

    var utils = _interopRequireWildcard(_utils)

    var _filtericeservers = require('./filtericeservers')

    var _rtcpeerconnectionShim = require('rtcpeerconnection-shim')

    var _rtcpeerconnectionShim2 = _interopRequireDefault(_rtcpeerconnectionShim)

    function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj } }

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window)

      if (window.RTCIceGatherer) {
        if (!window.RTCIceCandidate) {
          window.RTCIceCandidate = function RTCIceCandidate(args) {
            return args
          }
        }
        if (!window.RTCSessionDescription) {
          window.RTCSessionDescription = function RTCSessionDescription(args) {
            return args
          }
        }
        // this adds an additional event listener to MediaStrackTrack that signals
        // when a tracks enabled property was changed. Workaround for a bug in
        // addStream, see below. No longer required in 15025+
        if (browserDetails.version < 15025) {
          var origMSTEnabled = Object.getOwnPropertyDescriptor(window.MediaStreamTrack.prototype, 'enabled')
          Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
            set: function set(value) {
              origMSTEnabled.set.call(this, value)
              var ev = new Event('enabled')
              ev.enabled = value
              this.dispatchEvent(ev)
            },
            get: function get() {
              return origMSTEnabled.get()
            }
          })
        }
      }

      // ORTC defines the DTMF sender a bit different.
      // https://github.com/w3c/ortc/issues/714
      if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
          get: function get() {
            if (this._dtmf === undefined) {
              if (this.track.kind === 'audio') {
                this._dtmf = new window.RTCDtmfSender(this)
              } else if (this.track.kind === 'video') {
                this._dtmf = null
              }
            }
            return this._dtmf
          }
        })
      }
      // Edge currently only implements the RTCDtmfSender, not the
      // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
      if (window.RTCDtmfSender && !window.RTCDTMFSender) {
        window.RTCDTMFSender = window.RTCDtmfSender
      }

      var RTCPeerConnectionShim = (0, _rtcpeerconnectionShim2.default)(window, browserDetails.version)
      window.RTCPeerConnection = function RTCPeerConnection(config) {
        if (config && config.iceServers) {
          config.iceServers = (0, _filtericeservers.filterIceServers)(config.iceServers, browserDetails.version)
          utils.log('ICE servers after filtering:', config.iceServers)
        }
        return new RTCPeerConnectionShim(config)
      }
      window.RTCPeerConnection.prototype = RTCPeerConnectionShim.prototype
    }

    function shimReplaceTrack(window) {
      // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
      if (window.RTCRtpSender && !('replaceTrack' in window.RTCRtpSender.prototype)) {
        window.RTCRtpSender.prototype.replaceTrack = window.RTCRtpSender.prototype.setTrack
      }
    }
  }, { '../utils': 15, './filtericeservers': 8, './getdisplaymedia': 9, './getusermedia': 10, 'rtcpeerconnection-shim': 16 }], 8: [function(require, module, exports) {
    /*
 *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.filterIceServers = filterIceServers

    var _utils = require('../utils')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    // Edge does not like
    // 1) stun: filtered after 14393 unless ?transport=udp is present
    // 2) turn: that does not have all of turn:host:port?transport=udp
    // 3) turn: with ipv6 addresses
    // 4) turn: occurring muliple times
    function filterIceServers(iceServers, edgeVersion) {
      var hasTurn = false
      iceServers = JSON.parse(JSON.stringify(iceServers))
      return iceServers.filter(function(server) {
        if (server && (server.urls || server.url)) {
          var urls = server.urls || server.url
          if (server.url && !server.urls) {
            utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls')
          }
          var isString = typeof urls === 'string'
          if (isString) {
            urls = [urls]
          }
          urls = urls.filter(function(url) {
            // filter STUN unconditionally.
            if (url.indexOf('stun:') === 0) {
              return false
            }

            var validTurn = url.startsWith('turn') && !url.startsWith('turn:[') && url.includes('transport=udp')
            if (validTurn && !hasTurn) {
              hasTurn = true
              return true
            }
            return validTurn && !hasTurn
          })

          delete server.url
          server.urls = isString ? urls[0] : urls
          return !!urls.length
        }
      })
    }
  }, { '../utils': 15 }], 9: [function(require, module, exports) {
    /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = shimGetDisplayMedia
    function shimGetDisplayMedia(window) {
      if (!('getDisplayMedia' in window.navigator)) {
        return
      }
      if (!window.navigator.mediaDevices) {
        return
      }
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return
      }
      window.navigator.mediaDevices.getDisplayMedia = window.navigator.getDisplayMedia.bind(window.navigator)
    }
  }, {}], 10: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetUserMedia = shimGetUserMedia
    function shimGetUserMedia(window) {
      var navigator = window && window.navigator

      var shimError_ = function shimError_(e) {
        return {
          name: { PermissionDeniedError: 'NotAllowedError' }[e.name] || e.name,
          message: e.message,
          constraint: e.constraint,
          toString: function toString() {
            return this.name
          }
        }
      }

      // getUserMedia error shim.
      var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices)
      navigator.mediaDevices.getUserMedia = function(c) {
        return origGetUserMedia(c).catch(function(e) {
          return Promise.reject(shimError_(e))
        })
      }
    }
  }, {}], 11: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    var _getusermedia = require('./getusermedia')

    Object.defineProperty(exports, 'shimGetUserMedia', {
      enumerable: true,
      get: function get() {
        return _getusermedia.shimGetUserMedia
      }
    })

    var _getdisplaymedia = require('./getdisplaymedia')

    Object.defineProperty(exports, 'shimGetDisplayMedia', {
      enumerable: true,
      get: function get() {
        return _getdisplaymedia.shimGetDisplayMedia
      }
    })
    exports.shimOnTrack = shimOnTrack
    exports.shimPeerConnection = shimPeerConnection
    exports.shimSenderGetStats = shimSenderGetStats
    exports.shimReceiverGetStats = shimReceiverGetStats
    exports.shimRemoveStream = shimRemoveStream
    exports.shimRTCDataChannel = shimRTCDataChannel
    exports.shimAddTransceiver = shimAddTransceiver
    exports.shimCreateOffer = shimCreateOffer
    exports.shimCreateAnswer = shimCreateAnswer

    var _utils = require('../utils')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }) } else { obj[key] = value } return obj }

    function shimOnTrack(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
          get: function get() {
            return { receiver: this.receiver }
          }
        })
      }
    }

    function shimPeerConnection(window) {
      var browserDetails = utils.detectBrowser(window)

      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !(window.RTCPeerConnection || window.mozRTCPeerConnection)) {
        return // probably media.peerconnection.enabled=false in about:config
      }
      if (!window.RTCPeerConnection && window.mozRTCPeerConnection) {
        // very basic support for old versions.
        window.RTCPeerConnection = window.mozRTCPeerConnection
      }

      if (browserDetails.version < 53) {
        // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
        ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function(method) {
          var nativeMethod = window.RTCPeerConnection.prototype[method]
          var methodObj = _defineProperty({}, method, function() {
            arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0])
            return nativeMethod.apply(this, arguments)
          })
          window.RTCPeerConnection.prototype[method] = methodObj[method]
        })
      }

      // support for addIceCandidate(null or undefined)
      // as well as ignoring {sdpMid, candidate: ""}
      if (browserDetails.version < 68) {
        var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate
        window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
          if (!arguments[0]) {
            if (arguments[1]) {
              arguments[1].apply(null)
            }
            return Promise.resolve()
          }
          // Firefox 68+ emits and processes {candidate: "", ...}, ignore
          // in older versions.
          if (arguments[0] && arguments[0].candidate === '') {
            return Promise.resolve()
          }
          return nativeAddIceCandidate.apply(this, arguments)
        }
      }

      var modernStatsTypes = {
        inboundrtp: 'inbound-rtp',
        outboundrtp: 'outbound-rtp',
        candidatepair: 'candidate-pair',
        localcandidate: 'local-candidate',
        remotecandidate: 'remote-candidate'
      }

      var nativeGetStats = window.RTCPeerConnection.prototype.getStats
      window.RTCPeerConnection.prototype.getStats = function getStats() {
        var _arguments = Array.prototype.slice.call(arguments)
        var selector = _arguments[0]
        var onSucc = _arguments[1]
        var onErr = _arguments[2]

        return nativeGetStats.apply(this, [selector || null]).then(function(stats) {
          if (browserDetails.version < 53 && !onSucc) {
            // Shim only promise getStats with spec-hyphens in type names
            // Leave callback version alone; misc old uses of forEach before Map
            try {
              stats.forEach(function(stat) {
                stat.type = modernStatsTypes[stat.type] || stat.type
              })
            } catch (e) {
              if (e.name !== 'TypeError') {
                throw e
              }
              // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
              stats.forEach(function(stat, i) {
                stats.set(i, Object.assign({}, stat, {
                  type: modernStatsTypes[stat.type] || stat.type
                }))
              })
            }
          }
          return stats
        }).then(onSucc, onErr)
      }
    }

    function shimSenderGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
        return
      }
      if (window.RTCRtpSender && 'getStats' in window.RTCRtpSender.prototype) {
        return
      }
      var origGetSenders = window.RTCPeerConnection.prototype.getSenders
      if (origGetSenders) {
        window.RTCPeerConnection.prototype.getSenders = function getSenders() {
          var _this = this

          var senders = origGetSenders.apply(this, [])
          senders.forEach(function(sender) {
            sender._pc = _this
            return sender._pc
          })
          return senders
        }
      }

      var origAddTrack = window.RTCPeerConnection.prototype.addTrack
      if (origAddTrack) {
        window.RTCPeerConnection.prototype.addTrack = function addTrack() {
          var sender = origAddTrack.apply(this, arguments)
          sender._pc = this
          return sender
        }
      }
      window.RTCRtpSender.prototype.getStats = function getStats() {
        return this.track ? this._pc.getStats(this.track) : Promise.resolve(new Map())
      }
    }

    function shimReceiverGetStats(window) {
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
        return
      }
      if (window.RTCRtpSender && 'getStats' in window.RTCRtpReceiver.prototype) {
        return
      }
      var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers
      if (origGetReceivers) {
        window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
          var _this2 = this

          var receivers = origGetReceivers.apply(this, [])
          receivers.forEach(function(receiver) {
            receiver._pc = _this2
            return receiver._pc
          })
          return receivers
        }
      }
      utils.wrapPeerConnectionEvent(window, 'track', function(e) {
        e.receiver._pc = e.srcElement
        return e
      })
      window.RTCRtpReceiver.prototype.getStats = function getStats() {
        return this._pc.getStats(this.track)
      }
    }

    function shimRemoveStream(window) {
      if (!window.RTCPeerConnection || 'removeStream' in window.RTCPeerConnection.prototype) {
        return
      }
      window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
        var _this3 = this

        utils.deprecated('removeStream', 'removeTrack')
        this.getSenders().forEach(function(sender) {
          if (sender.track && stream.getTracks().includes(sender.track)) {
            _this3.removeTrack(sender)
          }
        })
      }
    }

    function shimRTCDataChannel(window) {
      // rename DataChannel to RTCDataChannel (native fix in FF60):
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1173851
      if (window.DataChannel && !window.RTCDataChannel) {
        window.RTCDataChannel = window.DataChannel
      }
    }

    function shimAddTransceiver(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return
      }
      var origAddTransceiver = window.RTCPeerConnection.prototype.addTransceiver
      if (origAddTransceiver) {
        window.RTCPeerConnection.prototype.addTransceiver = function addTransceiver() {
          this.setParametersPromises = []
          var initParameters = arguments[1]
          var shouldPerformCheck = initParameters && 'sendEncodings' in initParameters
          if (shouldPerformCheck) {
            // If sendEncodings params are provided, validate grammar
            initParameters.sendEncodings.forEach(function(encodingParam) {
              if ('rid' in encodingParam) {
                var ridRegex = /^[a-z0-9]{0,16}$/i
                if (!ridRegex.test(encodingParam.rid)) {
                  throw new TypeError('Invalid RID value provided.')
                }
              }
              if ('scaleResolutionDownBy' in encodingParam) {
                if (!(parseFloat(encodingParam.scaleResolutionDownBy) >= 1.0)) {
                  throw new RangeError('scale_resolution_down_by must be >= 1.0')
                }
              }
              if ('maxFramerate' in encodingParam) {
                if (!(parseFloat(encodingParam.maxFramerate) >= 0)) {
                  throw new RangeError('max_framerate must be >= 0.0')
                }
              }
            })
          }
          var transceiver = origAddTransceiver.apply(this, arguments)
          if (shouldPerformCheck) {
            // Check if the init options were applied. If not we do this in an
            // asynchronous way and save the promise reference in a global object.
            // This is an ugly hack, but at the same time is way more robust than
            // checking the sender parameters before and after the createOffer
            // Also note that after the createoffer we are not 100% sure that
            // the params were asynchronously applied so we might miss the
            // opportunity to recreate offer.
            var sender = transceiver.sender

            var params = sender.getParameters()
            if (!('encodings' in params)) {
              params.encodings = initParameters.sendEncodings
              this.setParametersPromises.push(sender.setParameters(params).catch(function() {}))
            }
          }
          return transceiver
        }
      }
    }

    function shimCreateOffer(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return
      }
      var origCreateOffer = window.RTCPeerConnection.prototype.createOffer
      window.RTCPeerConnection.prototype.createOffer = function createOffer() {
        var _this4 = this
        var _arguments2 = arguments

        if (this.setParametersPromises && this.setParametersPromises.length) {
          return Promise.all(this.setParametersPromises).then(function() {
            return origCreateOffer.apply(_this4, _arguments2)
          }).finally(function() {
            _this4.setParametersPromises = []
          })
        }
        return origCreateOffer.apply(this, arguments)
      }
    }

    function shimCreateAnswer(window) {
      // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
      // Firefox ignores the init sendEncodings options passed to addTransceiver
      // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
      if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
        return
      }
      var origCreateAnswer = window.RTCPeerConnection.prototype.createAnswer
      window.RTCPeerConnection.prototype.createAnswer = function createAnswer() {
        var _this5 = this
        var _arguments3 = arguments

        if (this.setParametersPromises && this.setParametersPromises.length) {
          return Promise.all(this.setParametersPromises).then(function() {
            return origCreateAnswer.apply(_this5, _arguments3)
          }).finally(function() {
            _this5.setParametersPromises = []
          })
        }
        return origCreateAnswer.apply(this, arguments)
      }
    }
  }, { '../utils': 15, './getdisplaymedia': 12, './getusermedia': 13 }], 12: [function(require, module, exports) {
    /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })
    exports.shimGetDisplayMedia = shimGetDisplayMedia
    function shimGetDisplayMedia(window, preferredMediaSource) {
      if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
        return
      }
      if (!window.navigator.mediaDevices) {
        return
      }
      window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
        if (!(constraints && constraints.video)) {
          var err = new DOMException('getDisplayMedia without video ' + 'constraints is undefined')
          err.name = 'NotFoundError'
          // from https://heycam.github.io/webidl/#idl-DOMException-error-names
          err.code = 8
          return Promise.reject(err)
        }
        if (constraints.video === true) {
          constraints.video = { mediaSource: preferredMediaSource }
        } else {
          constraints.video.mediaSource = preferredMediaSource
        }
        return window.navigator.mediaDevices.getUserMedia(constraints)
      }
    }
  }, {}], 13: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    exports.shimGetUserMedia = shimGetUserMedia

    var _utils = require('../utils')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function shimGetUserMedia(window) {
      var browserDetails = utils.detectBrowser(window)
      var navigator = window && window.navigator
      var MediaStreamTrack = window && window.MediaStreamTrack

      navigator.getUserMedia = function(constraints, onSuccess, onError) {
        // Replace Firefox 44+'s deprecation warning with unprefixed version.
        utils.deprecated('navigator.getUserMedia', 'navigator.mediaDevices.getUserMedia')
        navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError)
      }

      if (!(browserDetails.version > 55 && 'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
        var remap = function remap(obj, a, b) {
          if (a in obj && !(b in obj)) {
            obj[b] = obj[a]
            delete obj[a]
          }
        }

        var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices)
        navigator.mediaDevices.getUserMedia = function(c) {
          if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object' && _typeof(c.audio) === 'object') {
            c = JSON.parse(JSON.stringify(c))
            remap(c.audio, 'autoGainControl', 'mozAutoGainControl')
            remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression')
          }
          return nativeGetUserMedia(c)
        }

        if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
          var nativeGetSettings = MediaStreamTrack.prototype.getSettings
          MediaStreamTrack.prototype.getSettings = function() {
            var obj = nativeGetSettings.apply(this, arguments)
            remap(obj, 'mozAutoGainControl', 'autoGainControl')
            remap(obj, 'mozNoiseSuppression', 'noiseSuppression')
            return obj
          }
        }

        if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
          var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints
          MediaStreamTrack.prototype.applyConstraints = function(c) {
            if (this.kind === 'audio' && (typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object') {
              c = JSON.parse(JSON.stringify(c))
              remap(c, 'autoGainControl', 'mozAutoGainControl')
              remap(c, 'noiseSuppression', 'mozNoiseSuppression')
            }
            return nativeApplyConstraints.apply(this, [c])
          }
        }
      }
    }
  }, { '../utils': 15 }], 14: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    exports.shimLocalStreamsAPI = shimLocalStreamsAPI
    exports.shimRemoteStreamsAPI = shimRemoteStreamsAPI
    exports.shimCallbacksAPI = shimCallbacksAPI
    exports.shimGetUserMedia = shimGetUserMedia
    exports.shimConstraints = shimConstraints
    exports.shimRTCIceServerUrls = shimRTCIceServerUrls
    exports.shimTrackEventTransceiver = shimTrackEventTransceiver
    exports.shimCreateOfferLegacy = shimCreateOfferLegacy
    exports.shimAudioContext = shimAudioContext

    var _utils = require('../utils')

    var utils = _interopRequireWildcard(_utils)

    function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key] } } newObj.default = obj; return newObj } }

    function shimLocalStreamsAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return
      }
      if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
          if (!this._localStreams) {
            this._localStreams = []
          }
          return this._localStreams
        }
      }
      if (!('addStream' in window.RTCPeerConnection.prototype)) {
        var _addTrack = window.RTCPeerConnection.prototype.addTrack
        window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
          var _this = this

          if (!this._localStreams) {
            this._localStreams = []
          }
          if (!this._localStreams.includes(stream)) {
            this._localStreams.push(stream)
          }
          // Try to emulate Chrome's behaviour of adding in audio-video order.
          // Safari orders by track id.
          stream.getAudioTracks().forEach(function(track) {
            return _addTrack.call(_this, track, stream)
          })
          stream.getVideoTracks().forEach(function(track) {
            return _addTrack.call(_this, track, stream)
          })
        }

        window.RTCPeerConnection.prototype.addTrack = function addTrack(track) {
          var _this2 = this

          for (var _len = arguments.length, streams = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
            streams[_key - 1] = arguments[_key]
          }

          if (streams) {
            streams.forEach(function(stream) {
              if (!_this2._localStreams) {
                _this2._localStreams = [stream]
              } else if (!_this2._localStreams.includes(stream)) {
                _this2._localStreams.push(stream)
              }
            })
          }
          return _addTrack.apply(this, arguments)
        }
      }
      if (!('removeStream' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
          var _this3 = this

          if (!this._localStreams) {
            this._localStreams = []
          }
          var index = this._localStreams.indexOf(stream)
          if (index === -1) {
            return
          }
          this._localStreams.splice(index, 1)
          var tracks = stream.getTracks()
          this.getSenders().forEach(function(sender) {
            if (tracks.includes(sender.track)) {
              _this3.removeTrack(sender)
            }
          })
        }
      }
    }

    function shimRemoteStreamsAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return
      }
      if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
        window.RTCPeerConnection.prototype.getRemoteStreams = function getRemoteStreams() {
          return this._remoteStreams ? this._remoteStreams : []
        }
      }
      if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
        Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
          get: function get() {
            return this._onaddstream
          },
          set: function set(f) {
            var _this4 = this

            if (this._onaddstream) {
              this.removeEventListener('addstream', this._onaddstream)
              this.removeEventListener('track', this._onaddstreampoly)
            }
            this.addEventListener('addstream', this._onaddstream = f)
            this.addEventListener('track', this._onaddstreampoly = function(e) {
              e.streams.forEach(function(stream) {
                if (!_this4._remoteStreams) {
                  _this4._remoteStreams = []
                }
                if (_this4._remoteStreams.includes(stream)) {
                  return
                }
                _this4._remoteStreams.push(stream)
                var event = new Event('addstream')
                event.stream = stream
                _this4.dispatchEvent(event)
              })
            })
          }
        })
        var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription
        window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
          var pc = this
          if (!this._onaddstreampoly) {
            this.addEventListener('track', this._onaddstreampoly = function(e) {
              e.streams.forEach(function(stream) {
                if (!pc._remoteStreams) {
                  pc._remoteStreams = []
                }
                if (pc._remoteStreams.indexOf(stream) >= 0) {
                  return
                }
                pc._remoteStreams.push(stream)
                var event = new Event('addstream')
                event.stream = stream
                pc.dispatchEvent(event)
              })
            })
          }
          return origSetRemoteDescription.apply(pc, arguments)
        }
      }
    }

    function shimCallbacksAPI(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
        return
      }
      var prototype = window.RTCPeerConnection.prototype
      var origCreateOffer = prototype.createOffer
      var origCreateAnswer = prototype.createAnswer
      var setLocalDescription = prototype.setLocalDescription
      var setRemoteDescription = prototype.setRemoteDescription
      var addIceCandidate = prototype.addIceCandidate

      prototype.createOffer = function createOffer(successCallback, failureCallback) {
        var options = arguments.length >= 2 ? arguments[2] : arguments[0]
        var promise = origCreateOffer.apply(this, [options])
        if (!failureCallback) {
          return promise
        }
        promise.then(successCallback, failureCallback)
        return Promise.resolve()
      }

      prototype.createAnswer = function createAnswer(successCallback, failureCallback) {
        var options = arguments.length >= 2 ? arguments[2] : arguments[0]
        var promise = origCreateAnswer.apply(this, [options])
        if (!failureCallback) {
          return promise
        }
        promise.then(successCallback, failureCallback)
        return Promise.resolve()
      }

      var withCallback = function withCallback(description, successCallback, failureCallback) {
        var promise = setLocalDescription.apply(this, [description])
        if (!failureCallback) {
          return promise
        }
        promise.then(successCallback, failureCallback)
        return Promise.resolve()
      }
      prototype.setLocalDescription = withCallback

      withCallback = function withCallback(description, successCallback, failureCallback) {
        var promise = setRemoteDescription.apply(this, [description])
        if (!failureCallback) {
          return promise
        }
        promise.then(successCallback, failureCallback)
        return Promise.resolve()
      }
      prototype.setRemoteDescription = withCallback

      withCallback = function withCallback(candidate, successCallback, failureCallback) {
        var promise = addIceCandidate.apply(this, [candidate])
        if (!failureCallback) {
          return promise
        }
        promise.then(successCallback, failureCallback)
        return Promise.resolve()
      }
      prototype.addIceCandidate = withCallback
    }

    function shimGetUserMedia(window) {
      var navigator = window && window.navigator

      if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        // shim not needed in Safari 12.1
        var mediaDevices = navigator.mediaDevices
        var _getUserMedia = mediaDevices.getUserMedia.bind(mediaDevices)
        navigator.mediaDevices.getUserMedia = function(constraints) {
          return _getUserMedia(shimConstraints(constraints))
        }
      }

      if (!navigator.getUserMedia && navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        navigator.getUserMedia = function getUserMedia(constraints, cb, errcb) {
          navigator.mediaDevices.getUserMedia(constraints).then(cb, errcb)
        }
      }
    }

    function shimConstraints(constraints) {
      if (constraints && constraints.video !== undefined) {
        return Object.assign({}, constraints, { video: utils.compactObject(constraints.video) })
      }

      return constraints
    }

    function shimRTCIceServerUrls(window) {
      // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
      var OrigPeerConnection = window.RTCPeerConnection
      window.RTCPeerConnection = function RTCPeerConnection(pcConfig, pcConstraints) {
        if (pcConfig && pcConfig.iceServers) {
          var newIceServers = []
          for (var i = 0; i < pcConfig.iceServers.length; i++) {
            var server = pcConfig.iceServers[i]
            // eslint-disable-next-line no-prototype-builtins
            if (!server.hasOwnProperty('urls') && server.hasOwnProperty('url')) {
              utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls')
              server = JSON.parse(JSON.stringify(server))
              server.urls = server.url
              delete server.url
              newIceServers.push(server)
            } else {
              newIceServers.push(pcConfig.iceServers[i])
            }
          }
          pcConfig.iceServers = newIceServers
        }
        return new OrigPeerConnection(pcConfig, pcConstraints)
      }
      window.RTCPeerConnection.prototype = OrigPeerConnection.prototype
      // wrap static methods. Currently just generateCertificate.
      if ('generateCertificate' in window.RTCPeerConnection) {
        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
          get: function get() {
            return OrigPeerConnection.generateCertificate
          }
        })
      }
    }

    function shimTrackEventTransceiver(window) {
      // Add event.transceiver member over deprecated event.receiver
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
          get: function get() {
            return { receiver: this.receiver }
          }
        })
      }
    }

    function shimCreateOfferLegacy(window) {
      var origCreateOffer = window.RTCPeerConnection.prototype.createOffer
      window.RTCPeerConnection.prototype.createOffer = function createOffer(offerOptions) {
        if (offerOptions) {
          if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
            // support bit values
            offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio
          }
          var audioTransceiver = this.getTransceivers().find(function(transceiver) {
            return transceiver.receiver.track.kind === 'audio'
          })
          if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
            if (audioTransceiver.direction === 'sendrecv') {
              if (audioTransceiver.setDirection) {
                audioTransceiver.setDirection('sendonly')
              } else {
                audioTransceiver.direction = 'sendonly'
              }
            } else if (audioTransceiver.direction === 'recvonly') {
              if (audioTransceiver.setDirection) {
                audioTransceiver.setDirection('inactive')
              } else {
                audioTransceiver.direction = 'inactive'
              }
            }
          } else if (offerOptions.offerToReceiveAudio === true && !audioTransceiver) {
            this.addTransceiver('audio')
          }

          if (typeof offerOptions.offerToReceiveVideo !== 'undefined') {
            // support bit values
            offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo
          }
          var videoTransceiver = this.getTransceivers().find(function(transceiver) {
            return transceiver.receiver.track.kind === 'video'
          })
          if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
            if (videoTransceiver.direction === 'sendrecv') {
              if (videoTransceiver.setDirection) {
                videoTransceiver.setDirection('sendonly')
              } else {
                videoTransceiver.direction = 'sendonly'
              }
            } else if (videoTransceiver.direction === 'recvonly') {
              if (videoTransceiver.setDirection) {
                videoTransceiver.setDirection('inactive')
              } else {
                videoTransceiver.direction = 'inactive'
              }
            }
          } else if (offerOptions.offerToReceiveVideo === true && !videoTransceiver) {
            this.addTransceiver('video')
          }
        }
        return origCreateOffer.apply(this, arguments)
      }
    }

    function shimAudioContext(window) {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || window.AudioContext) {
        return
      }
      window.AudioContext = window.webkitAudioContext
    }
  }, { '../utils': 15 }], 15: [function(require, module, exports) {
    /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    Object.defineProperty(exports, '__esModule', {
      value: true
    })

    var _typeof = typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol' ? function(obj) { return typeof obj } : function(obj) { return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj }

    exports.extractVersion = extractVersion
    exports.wrapPeerConnectionEvent = wrapPeerConnectionEvent
    exports.disableLog = disableLog
    exports.disableWarnings = disableWarnings
    exports.log = log
    exports.deprecated = deprecated
    exports.detectBrowser = detectBrowser
    exports.compactObject = compactObject
    exports.walkStats = walkStats
    exports.filterStats = filterStats

    function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }) } else { obj[key] = value } return obj }

    var logDisabled_ = true
    var deprecationWarnings_ = true

    /**
 * Extract browser version out of the provided user agent string.
 *
 * @param {!string} uastring userAgent string.
 * @param {!string} expr Regular expression used as match criteria.
 * @param {!number} pos position in the version string to be returned.
 * @return {!number} browser version.
 */
    function extractVersion(uastring, expr, pos) {
      var match = uastring.match(expr)
      return match && match.length >= pos && parseInt(match[pos], 10)
    }

    // Wraps the peerconnection event eventNameToWrap in a function
    // which returns the modified event object (or false to prevent
    // the event).
    function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
      if (!window.RTCPeerConnection) {
        return
      }
      var proto = window.RTCPeerConnection.prototype
      var nativeAddEventListener = proto.addEventListener
      proto.addEventListener = function(nativeEventName, cb) {
        if (nativeEventName !== eventNameToWrap) {
          return nativeAddEventListener.apply(this, arguments)
        }
        var wrappedCallback = function wrappedCallback(e) {
          var modifiedEvent = wrapper(e)
          if (modifiedEvent) {
            cb(modifiedEvent)
          }
        }
        this._eventMap = this._eventMap || {}
        this._eventMap[cb] = wrappedCallback
        return nativeAddEventListener.apply(this, [nativeEventName, wrappedCallback])
      }

      var nativeRemoveEventListener = proto.removeEventListener
      proto.removeEventListener = function(nativeEventName, cb) {
        if (nativeEventName !== eventNameToWrap || !this._eventMap || !this._eventMap[cb]) {
          return nativeRemoveEventListener.apply(this, arguments)
        }
        var unwrappedCb = this._eventMap[cb]
        delete this._eventMap[cb]
        return nativeRemoveEventListener.apply(this, [nativeEventName, unwrappedCb])
      }

      Object.defineProperty(proto, 'on' + eventNameToWrap, {
        get: function get() {
          return this['_on' + eventNameToWrap]
        },
        set: function set(cb) {
          if (this['_on' + eventNameToWrap]) {
            this.removeEventListener(eventNameToWrap, this['_on' + eventNameToWrap])
            delete this['_on' + eventNameToWrap]
          }
          if (cb) {
            this.addEventListener(eventNameToWrap, this['_on' + eventNameToWrap] = cb)
          }
        },

        enumerable: true,
        configurable: true
      })
    }

    function disableLog(bool) {
      if (typeof bool !== 'boolean') {
        return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.')
      }
      logDisabled_ = bool
      return bool ? 'adapter.js logging disabled' : 'adapter.js logging enabled'
    }

    /**
 * Disable or enable deprecation warnings
 * @param {!boolean} bool set to true to disable warnings.
 */
    function disableWarnings(bool) {
      if (typeof bool !== 'boolean') {
        return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.')
      }
      deprecationWarnings_ = !bool
      return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled')
    }

    function log() {
      if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object') {
        if (logDisabled_) {
          return
        }
        if (typeof console !== 'undefined' && typeof console.log === 'function') {
          console.log.apply(console, arguments)
        }
      }
    }

    /**
 * Shows a deprecation warning suggesting the modern and spec-compatible API.
 */
    function deprecated(oldMethod, newMethod) {
      if (!deprecationWarnings_) {
        return
      }
      console.warn(oldMethod + ' is deprecated, please use ' + newMethod + ' instead.')
    }

    /**
 * Browser detector.
 *
 * @return {object} result containing browser and version
 *     properties.
 */
    function detectBrowser(window) {
      var navigator = window.navigator

      // Returned result object.

      var result = { browser: null, version: null }

      // Fail early if it's not a browser
      if (typeof window === 'undefined' || !window.navigator) {
        result.browser = 'Not a browser.'
        return result
      }

      if (navigator.userAgent.toLowerCase().indexOf(' electron/') > -1) {
        result.browser = 'electron'
        result.version = extractVersion(navigator.userAgent, /electron\/(\d+)\./, 2)
      } else if (navigator.mozGetUserMedia) {
        // Firefox.
        result.browser = 'firefox'
        result.version = extractVersion(navigator.userAgent, /Firefox\/(\d+)\./, 1)
      } else if (navigator.webkitGetUserMedia || window.isSecureContext === false && window.webkitRTCPeerConnection && !window.RTCIceGatherer) {
        // Chrome, Chromium, Webview, Opera.
        // Version matches Chrome/WebRTC version.
        // Chrome 74 removed webkitGetUserMedia on http as well so we need the
        // more complicated fallback to webkitRTCPeerConnection.
        result.browser = 'chrome'
        result.version = extractVersion(navigator.userAgent, /Chrom(e|ium)\/(\d+)\./, 2)
      } else if (navigator.mediaDevices && navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
        // Edge.
        result.browser = 'edge'
        result.version = extractVersion(navigator.userAgent, /Edge\/(\d+).(\d+)$/, 2)
      } else if (window.RTCPeerConnection && navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
        // Safari.
        result.browser = 'safari'
        result.version = extractVersion(navigator.userAgent, /AppleWebKit\/(\d+)\./, 1)
        result.supportsUnifiedPlan = window.RTCRtpTransceiver && 'currentDirection' in window.RTCRtpTransceiver.prototype
      } else {
        // Default fallthrough: not supported.
        result.browser = 'Not a supported browser.'
        return result
      }

      return result
    }

    /**
 * Checks if something is an object.
 *
 * @param {*} val The something you want to check.
 * @return true if val is an object, false otherwise.
 */
    function isObject(val) {
      return Object.prototype.toString.call(val) === '[object Object]'
    }

    /**
 * Remove all empty objects and undefined values
 * from a nested object -- an enhanced and vanilla version
 * of Lodash's `compact`.
 */
    function compactObject(data) {
      if (!isObject(data)) {
        return data
      }

      return Object.keys(data).reduce(function(accumulator, key) {
        var isObj = isObject(data[key])
        var value = isObj ? compactObject(data[key]) : data[key]
        var isEmptyObject = isObj && !Object.keys(value).length
        if (value === undefined || isEmptyObject) {
          return accumulator
        }
        return Object.assign(accumulator, _defineProperty({}, key, value))
      }, {})
    }

    /* iterates the stats graph recursively. */
    function walkStats(stats, base, resultSet) {
      if (!base || resultSet.has(base.id)) {
        return
      }
      resultSet.set(base.id, base)
      Object.keys(base).forEach(function(name) {
        if (name.endsWith('Id')) {
          walkStats(stats, stats.get(base[name]), resultSet)
        } else if (name.endsWith('Ids')) {
          base[name].forEach(function(id) {
            walkStats(stats, stats.get(id), resultSet)
          })
        }
      })
    }

    /* filter getStats for a sender/receiver track. */
    function filterStats(result, track, outbound) {
      var streamStatsType = outbound ? 'outbound-rtp' : 'inbound-rtp'
      var filteredResult = new Map()
      if (track === null) {
        return filteredResult
      }
      var trackStats = []
      result.forEach(function(value) {
        if (value.type === 'track' && value.trackIdentifier === track.id) {
          trackStats.push(value)
        }
      })
      trackStats.forEach(function(trackStat) {
        result.forEach(function(stats) {
          if (stats.type === streamStatsType && stats.trackId === trackStat.id) {
            walkStats(result, stats, filteredResult)
          }
        })
      })
      return filteredResult
    }
  }, {}], 16: [function(require, module, exports) {
    /*
 *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
    /* eslint-env node */
    'use strict'

    var SDPUtils = require('sdp')

    function fixStatsType(stat) {
      return {
        inboundrtp: 'inbound-rtp',
        outboundrtp: 'outbound-rtp',
        candidatepair: 'candidate-pair',
        localcandidate: 'local-candidate',
        remotecandidate: 'remote-candidate'
      }[stat.type] || stat.type
    }

    function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
      var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps)

      // Map ICE parameters (ufrag, pwd) to SDP.
      sdp += SDPUtils.writeIceParameters(
        transceiver.iceGatherer.getLocalParameters())

      // Map DTLS parameters to SDP.
      sdp += SDPUtils.writeDtlsParameters(
        transceiver.dtlsTransport.getLocalParameters(),
        type === 'offer' ? 'actpass' : dtlsRole || 'active')

      sdp += 'a=mid:' + transceiver.mid + '\r\n'

      if (transceiver.rtpSender && transceiver.rtpReceiver) {
        sdp += 'a=sendrecv\r\n'
      } else if (transceiver.rtpSender) {
        sdp += 'a=sendonly\r\n'
      } else if (transceiver.rtpReceiver) {
        sdp += 'a=recvonly\r\n'
      } else {
        sdp += 'a=inactive\r\n'
      }

      if (transceiver.rtpSender) {
        var trackId = transceiver.rtpSender._initialTrackId ||
        transceiver.rtpSender.track.id
        transceiver.rtpSender._initialTrackId = trackId
        // spec.
        var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
        trackId + '\r\n'
        sdp += 'a=' + msid
        // for Chrome. Legacy should no longer be required.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
        ' ' + msid

        // RTX
        if (transceiver.sendEncodingParameters[0].rtx) {
          sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
          ' ' + msid
          sdp += 'a=ssrc-group:FID ' +
          transceiver.sendEncodingParameters[0].ssrc + ' ' +
          transceiver.sendEncodingParameters[0].rtx.ssrc +
          '\r\n'
        }
      }
      // FIXME: this should be written by writeRtpDescription.
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
      ' cname:' + SDPUtils.localCName + '\r\n'
      if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
        ' cname:' + SDPUtils.localCName + '\r\n'
      }
      return sdp
    }

    // Edge does not like
    // 1) stun: filtered after 14393 unless ?transport=udp is present
    // 2) turn: that does not have all of turn:host:port?transport=udp
    // 3) turn: with ipv6 addresses
    // 4) turn: occurring muliple times
    function filterIceServers(iceServers, edgeVersion) {
      var hasTurn = false
      iceServers = JSON.parse(JSON.stringify(iceServers))
      return iceServers.filter(function(server) {
        if (server && (server.urls || server.url)) {
          var urls = server.urls || server.url
          if (server.url && !server.urls) {
            console.warn('RTCIceServer.url is deprecated! Use urls instead.')
          }
          var isString = typeof urls === 'string'
          if (isString) {
            urls = [urls]
          }
          urls = urls.filter(function(url) {
            var validTurn = url.indexOf('turn:') === 0 &&
            url.indexOf('transport=udp') !== -1 &&
            url.indexOf('turn:[') === -1 &&
            !hasTurn

            if (validTurn) {
              hasTurn = true
              return true
            }
            return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
            url.indexOf('?transport=udp') === -1
          })

          delete server.url
          server.urls = isString ? urls[0] : urls
          return !!urls.length
        }
      })
    }

    // Determines the intersection of local and remote capabilities.
    function getCommonCapabilities(localCapabilities, remoteCapabilities) {
      var commonCapabilities = {
        codecs: [],
        headerExtensions: [],
        fecMechanisms: []
      }

      var findCodecByPayloadType = function(pt, codecs) {
        pt = parseInt(pt, 10)
        for (var i = 0; i < codecs.length; i++) {
          if (codecs[i].payloadType === pt ||
          codecs[i].preferredPayloadType === pt) {
            return codecs[i]
          }
        }
      }

      var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
        var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs)
        var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs)
        return lCodec && rCodec &&
        lCodec.name.toLowerCase() === rCodec.name.toLowerCase()
      }

      localCapabilities.codecs.forEach(function(lCodec) {
        for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
          var rCodec = remoteCapabilities.codecs[i]
          if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
          lCodec.clockRate === rCodec.clockRate) {
            if (lCodec.name.toLowerCase() === 'rtx' &&
            lCodec.parameters && rCodec.parameters.apt) {
              // for RTX we need to find the local rtx that has a apt
              // which points to the same local codec as the remote one.
              if (!rtxCapabilityMatches(lCodec, rCodec,
                localCapabilities.codecs, remoteCapabilities.codecs)) {
                continue
              }
            }
            rCodec = JSON.parse(JSON.stringify(rCodec)) // deepcopy
            // number of channels is the highest common number of channels
            rCodec.numChannels = Math.min(lCodec.numChannels,
              rCodec.numChannels)
            // push rCodec so we reply with offerer payload type
            commonCapabilities.codecs.push(rCodec)

            // determine common feedback mechanisms
            rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
              for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
                if (lCodec.rtcpFeedback[j].type === fb.type &&
                lCodec.rtcpFeedback[j].parameter === fb.parameter) {
                  return true
                }
              }
              return false
            })
            // FIXME: also need to determine .parameters
            //  see https://github.com/openpeer/ortc/issues/569
            break
          }
        }
      })

      localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
        for (var i = 0; i < remoteCapabilities.headerExtensions.length;
          i++) {
          var rHeaderExtension = remoteCapabilities.headerExtensions[i]
          if (lHeaderExtension.uri === rHeaderExtension.uri) {
            commonCapabilities.headerExtensions.push(rHeaderExtension)
            break
          }
        }
      })

      // FIXME: fecMechanisms
      return commonCapabilities
    }

    // is action=setLocalDescription with type allowed in signalingState
    function isActionAllowedInSignalingState(action, type, signalingState) {
      return {
        offer: {
          setLocalDescription: ['stable', 'have-local-offer'],
          setRemoteDescription: ['stable', 'have-remote-offer']
        },
        answer: {
          setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
          setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
        }
      }[type][action].indexOf(signalingState) !== -1
    }

    function maybeAddCandidate(iceTransport, candidate) {
      // Edge's internal representation adds some fields therefore
      // not all fieldѕ are taken into account.
      var alreadyAdded = iceTransport.getRemoteCandidates()
        .find(function(remoteCandidate) {
          return candidate.foundation === remoteCandidate.foundation &&
            candidate.ip === remoteCandidate.ip &&
            candidate.port === remoteCandidate.port &&
            candidate.priority === remoteCandidate.priority &&
            candidate.protocol === remoteCandidate.protocol &&
            candidate.type === remoteCandidate.type
        })
      if (!alreadyAdded) {
        iceTransport.addRemoteCandidate(candidate)
      }
      return !alreadyAdded
    }

    function makeError(name, description) {
      var e = new Error(description)
      e.name = name
      // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
      e.code = {
        NotSupportedError: 9,
        InvalidStateError: 11,
        InvalidAccessError: 15,
        TypeError: undefined,
        OperationError: undefined
      }[name]
      return e
    }

    module.exports = function(window, edgeVersion) {
      // https://w3c.github.io/mediacapture-main/#mediastream
      // Helper function to add the track to the stream and
      // dispatch the event ourselves.
      function addTrackToStreamAndFireEvent(track, stream) {
        stream.addTrack(track)
        stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack',
          { track: track }))
      }

      function removeTrackFromStreamAndFireEvent(track, stream) {
        stream.removeTrack(track)
        stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack',
          { track: track }))
      }

      function fireAddTrack(pc, track, receiver, streams) {
        var trackEvent = new Event('track')
        trackEvent.track = track
        trackEvent.receiver = receiver
        trackEvent.transceiver = { receiver: receiver }
        trackEvent.streams = streams
        window.setTimeout(function() {
          pc._dispatchEvent('track', trackEvent)
        })
      }

      var RTCPeerConnection = function(config) {
        var pc = this

        var _eventTarget = document.createDocumentFragment();
        ['addEventListener', 'removeEventListener', 'dispatchEvent']
          .forEach(function(method) {
            pc[method] = _eventTarget[method].bind(_eventTarget)
          })

        this.canTrickleIceCandidates = null

        this.needNegotiation = false

        this.localStreams = []
        this.remoteStreams = []

        this._localDescription = null
        this._remoteDescription = null

        this.signalingState = 'stable'
        this.iceConnectionState = 'new'
        this.connectionState = 'new'
        this.iceGatheringState = 'new'

        config = JSON.parse(JSON.stringify(config || {}))

        this.usingBundle = config.bundlePolicy === 'max-bundle'
        if (config.rtcpMuxPolicy === 'negotiate') {
          throw (makeError('NotSupportedError',
            'rtcpMuxPolicy \'negotiate\' is not supported'))
        } else if (!config.rtcpMuxPolicy) {
          config.rtcpMuxPolicy = 'require'
        }

        switch (config.iceTransportPolicy) {
          case 'all':
          case 'relay':
            break
          default:
            config.iceTransportPolicy = 'all'
            break
        }

        switch (config.bundlePolicy) {
          case 'balanced':
          case 'max-compat':
          case 'max-bundle':
            break
          default:
            config.bundlePolicy = 'balanced'
            break
        }

        config.iceServers = filterIceServers(config.iceServers || [], edgeVersion)

        this._iceGatherers = []
        if (config.iceCandidatePoolSize) {
          for (var i = config.iceCandidatePoolSize; i > 0; i--) {
            this._iceGatherers.push(new window.RTCIceGatherer({
              iceServers: config.iceServers,
              gatherPolicy: config.iceTransportPolicy
            }))
          }
        } else {
          config.iceCandidatePoolSize = 0
        }

        this._config = config

        // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
        // everything that is needed to describe a SDP m-line.
        this.transceivers = []

        this._sdpSessionId = SDPUtils.generateSessionId()
        this._sdpSessionVersion = 0

        this._dtlsRole = undefined // role for a=setup to use in answers.

        this._isClosed = false
      }

      Object.defineProperty(RTCPeerConnection.prototype, 'localDescription', {
        configurable: true,
        get: function() {
          return this._localDescription
        }
      })
      Object.defineProperty(RTCPeerConnection.prototype, 'remoteDescription', {
        configurable: true,
        get: function() {
          return this._remoteDescription
        }
      })

      // set up event handlers on prototype
      RTCPeerConnection.prototype.onicecandidate = null
      RTCPeerConnection.prototype.onaddstream = null
      RTCPeerConnection.prototype.ontrack = null
      RTCPeerConnection.prototype.onremovestream = null
      RTCPeerConnection.prototype.onsignalingstatechange = null
      RTCPeerConnection.prototype.oniceconnectionstatechange = null
      RTCPeerConnection.prototype.onconnectionstatechange = null
      RTCPeerConnection.prototype.onicegatheringstatechange = null
      RTCPeerConnection.prototype.onnegotiationneeded = null
      RTCPeerConnection.prototype.ondatachannel = null

      RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
        if (this._isClosed) {
          return
        }
        this.dispatchEvent(event)
        if (typeof this['on' + name] === 'function') {
          this['on' + name](event)
        }
      }

      RTCPeerConnection.prototype._emitGatheringStateChange = function() {
        var event = new Event('icegatheringstatechange')
        this._dispatchEvent('icegatheringstatechange', event)
      }

      RTCPeerConnection.prototype.getConfiguration = function() {
        return this._config
      }

      RTCPeerConnection.prototype.getLocalStreams = function() {
        return this.localStreams
      }

      RTCPeerConnection.prototype.getRemoteStreams = function() {
        return this.remoteStreams
      }

      // internal helper to create a transceiver object.
      // (which is not yet the same as the WebRTC 1.0 transceiver)
      RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
        var hasBundleTransport = this.transceivers.length > 0
        var transceiver = {
          track: null,
          iceGatherer: null,
          iceTransport: null,
          dtlsTransport: null,
          localCapabilities: null,
          remoteCapabilities: null,
          rtpSender: null,
          rtpReceiver: null,
          kind: kind,
          mid: null,
          sendEncodingParameters: null,
          recvEncodingParameters: null,
          stream: null,
          associatedRemoteMediaStreams: [],
          wantReceive: true
        }
        if (this.usingBundle && hasBundleTransport) {
          transceiver.iceTransport = this.transceivers[0].iceTransport
          transceiver.dtlsTransport = this.transceivers[0].dtlsTransport
        } else {
          var transports = this._createIceAndDtlsTransports()
          transceiver.iceTransport = transports.iceTransport
          transceiver.dtlsTransport = transports.dtlsTransport
        }
        if (!doNotAdd) {
          this.transceivers.push(transceiver)
        }
        return transceiver
      }

      RTCPeerConnection.prototype.addTrack = function(track, stream) {
        if (this._isClosed) {
          throw makeError('InvalidStateError',
            'Attempted to call addTrack on a closed peerconnection.')
        }

        var alreadyExists = this.transceivers.find(function(s) {
          return s.track === track
        })

        if (alreadyExists) {
          throw makeError('InvalidAccessError', 'Track already exists.')
        }

        var transceiver
        for (var i = 0; i < this.transceivers.length; i++) {
          if (!this.transceivers[i].track &&
          this.transceivers[i].kind === track.kind) {
            transceiver = this.transceivers[i]
          }
        }
        if (!transceiver) {
          transceiver = this._createTransceiver(track.kind)
        }

        this._maybeFireNegotiationNeeded()

        if (this.localStreams.indexOf(stream) === -1) {
          this.localStreams.push(stream)
        }

        transceiver.track = track
        transceiver.stream = stream
        transceiver.rtpSender = new window.RTCRtpSender(track,
          transceiver.dtlsTransport)
        return transceiver.rtpSender
      }

      RTCPeerConnection.prototype.addStream = function(stream) {
        var pc = this
        if (edgeVersion >= 15025) {
          stream.getTracks().forEach(function(track) {
            pc.addTrack(track, stream)
          })
        } else {
          // Clone is necessary for local demos mostly, attaching directly
          // to two different senders does not work (build 10547).
          // Fixed in 15025 (or earlier)
          var clonedStream = stream.clone()
          stream.getTracks().forEach(function(track, idx) {
            var clonedTrack = clonedStream.getTracks()[idx]
            track.addEventListener('enabled', function(event) {
              clonedTrack.enabled = event.enabled
            })
          })
          clonedStream.getTracks().forEach(function(track) {
            pc.addTrack(track, clonedStream)
          })
        }
      }

      RTCPeerConnection.prototype.removeTrack = function(sender) {
        if (this._isClosed) {
          throw makeError('InvalidStateError',
            'Attempted to call removeTrack on a closed peerconnection.')
        }

        if (!(sender instanceof window.RTCRtpSender)) {
          throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
          'does not implement interface RTCRtpSender.')
        }

        var transceiver = this.transceivers.find(function(t) {
          return t.rtpSender === sender
        })

        if (!transceiver) {
          throw makeError('InvalidAccessError',
            'Sender was not created by this connection.')
        }
        var stream = transceiver.stream

        transceiver.rtpSender.stop()
        transceiver.rtpSender = null
        transceiver.track = null
        transceiver.stream = null

        // remove the stream from the set of local streams
        var localStreams = this.transceivers.map(function(t) {
          return t.stream
        })
        if (localStreams.indexOf(stream) === -1 &&
        this.localStreams.indexOf(stream) > -1) {
          this.localStreams.splice(this.localStreams.indexOf(stream), 1)
        }

        this._maybeFireNegotiationNeeded()
      }

      RTCPeerConnection.prototype.removeStream = function(stream) {
        var pc = this
        stream.getTracks().forEach(function(track) {
          var sender = pc.getSenders().find(function(s) {
            return s.track === track
          })
          if (sender) {
            pc.removeTrack(sender)
          }
        })
      }

      RTCPeerConnection.prototype.getSenders = function() {
        return this.transceivers.filter(function(transceiver) {
          return !!transceiver.rtpSender
        })
          .map(function(transceiver) {
            return transceiver.rtpSender
          })
      }

      RTCPeerConnection.prototype.getReceivers = function() {
        return this.transceivers.filter(function(transceiver) {
          return !!transceiver.rtpReceiver
        })
          .map(function(transceiver) {
            return transceiver.rtpReceiver
          })
      }

      RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
        usingBundle) {
        var pc = this
        if (usingBundle && sdpMLineIndex > 0) {
          return this.transceivers[0].iceGatherer
        } else if (this._iceGatherers.length) {
          return this._iceGatherers.shift()
        }
        var iceGatherer = new window.RTCIceGatherer({
          iceServers: this._config.iceServers,
          gatherPolicy: this._config.iceTransportPolicy
        })
        Object.defineProperty(iceGatherer, 'state',
          { value: 'new', writable: true }
        )

        this.transceivers[sdpMLineIndex].bufferedCandidateEvents = []
        this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
          var end = !event.candidate || Object.keys(event.candidate).length === 0
          // polyfill since RTCIceGatherer.state is not implemented in
          // Edge 10547 yet.
          iceGatherer.state = end ? 'completed' : 'gathering'
          if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
            pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event)
          }
        }
        iceGatherer.addEventListener('localcandidate',
          this.transceivers[sdpMLineIndex].bufferCandidates)
        return iceGatherer
      }

      // start gathering from an RTCIceGatherer.
      RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
        var pc = this
        var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer
        if (iceGatherer.onlocalcandidate) {
          return
        }
        var bufferedCandidateEvents =
      this.transceivers[sdpMLineIndex].bufferedCandidateEvents
        this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null
        iceGatherer.removeEventListener('localcandidate',
          this.transceivers[sdpMLineIndex].bufferCandidates)
        iceGatherer.onlocalcandidate = function(evt) {
          if (pc.usingBundle && sdpMLineIndex > 0) {
            // if we know that we use bundle we can drop candidates with
            // ѕdpMLineIndex > 0. If we don't do this then our state gets
            // confused since we dispose the extra ice gatherer.
            return
          }
          var event = new Event('icecandidate')
          event.candidate = { sdpMid: mid, sdpMLineIndex: sdpMLineIndex }

          var cand = evt.candidate
          // Edge emits an empty object for RTCIceCandidateComplete‥
          var end = !cand || Object.keys(cand).length === 0
          if (end) {
            // polyfill since RTCIceGatherer.state is not implemented in
            // Edge 10547 yet.
            if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
              iceGatherer.state = 'completed'
            }
          } else {
            if (iceGatherer.state === 'new') {
              iceGatherer.state = 'gathering'
            }
            // RTCIceCandidate doesn't have a component, needs to be added
            cand.component = 1
            // also the usernameFragment. TODO: update SDP to take both variants.
            cand.ufrag = iceGatherer.getLocalParameters().usernameFragment

            var serializedCandidate = SDPUtils.writeCandidate(cand)
            event.candidate = Object.assign(event.candidate,
              SDPUtils.parseCandidate(serializedCandidate))

            event.candidate.candidate = serializedCandidate
            event.candidate.toJSON = function() {
              return {
                candidate: event.candidate.candidate,
                sdpMid: event.candidate.sdpMid,
                sdpMLineIndex: event.candidate.sdpMLineIndex,
                usernameFragment: event.candidate.usernameFragment
              }
            }
          }

          // update local description.
          var sections = SDPUtils.getMediaSections(pc._localDescription.sdp)
          if (!end) {
            sections[event.candidate.sdpMLineIndex] +=
            'a=' + event.candidate.candidate + '\r\n'
          } else {
            sections[event.candidate.sdpMLineIndex] +=
            'a=end-of-candidates\r\n'
          }
          pc._localDescription.sdp =
          SDPUtils.getDescription(pc._localDescription.sdp) +
          sections.join('')
          var complete = pc.transceivers.every(function(transceiver) {
            return transceiver.iceGatherer &&
            transceiver.iceGatherer.state === 'completed'
          })

          if (pc.iceGatheringState !== 'gathering') {
            pc.iceGatheringState = 'gathering'
            pc._emitGatheringStateChange()
          }

          // Emit candidate. Also emit null candidate when all gatherers are
          // complete.
          if (!end) {
            pc._dispatchEvent('icecandidate', event)
          }
          if (complete) {
            pc._dispatchEvent('icecandidate', new Event('icecandidate'))
            pc.iceGatheringState = 'complete'
            pc._emitGatheringStateChange()
          }
        }

        // emit already gathered candidates.
        window.setTimeout(function() {
          bufferedCandidateEvents.forEach(function(e) {
            iceGatherer.onlocalcandidate(e)
          })
        }, 0)
      }

      // Create ICE transport and DTLS transport.
      RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
        var pc = this
        var iceTransport = new window.RTCIceTransport(null)
        iceTransport.onicestatechange = function() {
          pc._updateIceConnectionState()
          pc._updateConnectionState()
        }

        var dtlsTransport = new window.RTCDtlsTransport(iceTransport)
        dtlsTransport.ondtlsstatechange = function() {
          pc._updateConnectionState()
        }
        dtlsTransport.onerror = function() {
          // onerror does not set state to failed by itself.
          Object.defineProperty(dtlsTransport, 'state',
            { value: 'failed', writable: true })
          pc._updateConnectionState()
        }

        return {
          iceTransport: iceTransport,
          dtlsTransport: dtlsTransport
        }
      }

      // Destroy ICE gatherer, ICE transport and DTLS transport.
      // Without triggering the callbacks.
      RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
        sdpMLineIndex) {
        var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer
        if (iceGatherer) {
          delete iceGatherer.onlocalcandidate
          delete this.transceivers[sdpMLineIndex].iceGatherer
        }
        var iceTransport = this.transceivers[sdpMLineIndex].iceTransport
        if (iceTransport) {
          delete iceTransport.onicestatechange
          delete this.transceivers[sdpMLineIndex].iceTransport
        }
        var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport
        if (dtlsTransport) {
          delete dtlsTransport.ondtlsstatechange
          delete dtlsTransport.onerror
          delete this.transceivers[sdpMLineIndex].dtlsTransport
        }
      }

      // Start the RTP Sender and Receiver for a transceiver.
      RTCPeerConnection.prototype._transceive = function(transceiver,
        send, recv) {
        var params = getCommonCapabilities(transceiver.localCapabilities,
          transceiver.remoteCapabilities)
        if (send && transceiver.rtpSender) {
          params.encodings = transceiver.sendEncodingParameters
          params.rtcp = {
            cname: SDPUtils.localCName,
            compound: transceiver.rtcpParameters.compound
          }
          if (transceiver.recvEncodingParameters.length) {
            params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc
          }
          transceiver.rtpSender.send(params)
        }
        if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
          // remove RTX field in Edge 14942
          if (transceiver.kind === 'video' &&
          transceiver.recvEncodingParameters &&
          edgeVersion < 15019) {
            transceiver.recvEncodingParameters.forEach(function(p) {
              delete p.rtx
            })
          }
          if (transceiver.recvEncodingParameters.length) {
            params.encodings = transceiver.recvEncodingParameters
          } else {
            params.encodings = [{}]
          }
          params.rtcp = {
            compound: transceiver.rtcpParameters.compound
          }
          if (transceiver.rtcpParameters.cname) {
            params.rtcp.cname = transceiver.rtcpParameters.cname
          }
          if (transceiver.sendEncodingParameters.length) {
            params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc
          }
          transceiver.rtpReceiver.receive(params)
        }
      }

      RTCPeerConnection.prototype.setLocalDescription = function(description) {
        var pc = this

        // Note: pranswer is not supported.
        if (['offer', 'answer'].indexOf(description.type) === -1) {
          return Promise.reject(makeError('TypeError',
            'Unsupported type "' + description.type + '"'))
        }

        if (!isActionAllowedInSignalingState('setLocalDescription',
          description.type, pc.signalingState) || pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
            'Can not set local ' + description.type +
          ' in state ' + pc.signalingState))
        }

        var sections
        var sessionpart
        if (description.type === 'offer') {
          // VERY limited support for SDP munging. Limited to:
          // * changing the order of codecs
          sections = SDPUtils.splitSections(description.sdp)
          sessionpart = sections.shift()
          sections.forEach(function(mediaSection, sdpMLineIndex) {
            var caps = SDPUtils.parseRtpParameters(mediaSection)
            pc.transceivers[sdpMLineIndex].localCapabilities = caps
          })

          pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
            pc._gather(transceiver.mid, sdpMLineIndex)
          })
        } else if (description.type === 'answer') {
          sections = SDPUtils.splitSections(pc._remoteDescription.sdp)
          sessionpart = sections.shift()
          var isIceLite = SDPUtils.matchPrefix(sessionpart,
            'a=ice-lite').length > 0
          sections.forEach(function(mediaSection, sdpMLineIndex) {
            var transceiver = pc.transceivers[sdpMLineIndex]
            var iceGatherer = transceiver.iceGatherer
            var iceTransport = transceiver.iceTransport
            var dtlsTransport = transceiver.dtlsTransport
            var localCapabilities = transceiver.localCapabilities
            var remoteCapabilities = transceiver.remoteCapabilities

            // treat bundle-only as not-rejected.
            var rejected = SDPUtils.isRejected(mediaSection) &&
            SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0

            if (!rejected && !transceiver.rejected) {
              var remoteIceParameters = SDPUtils.getIceParameters(
                mediaSection, sessionpart)
              var remoteDtlsParameters = SDPUtils.getDtlsParameters(
                mediaSection, sessionpart)
              if (isIceLite) {
                remoteDtlsParameters.role = 'server'
              }

              if (!pc.usingBundle || sdpMLineIndex === 0) {
                pc._gather(transceiver.mid, sdpMLineIndex)
                if (iceTransport.state === 'new') {
                  iceTransport.start(iceGatherer, remoteIceParameters,
                    isIceLite ? 'controlling' : 'controlled')
                }
                if (dtlsTransport.state === 'new') {
                  dtlsTransport.start(remoteDtlsParameters)
                }
              }

              // Calculate intersection of capabilities.
              var params = getCommonCapabilities(localCapabilities,
                remoteCapabilities)

              // Start the RTCRtpSender. The RTCRtpReceiver for this
              // transceiver has already been started in setRemoteDescription.
              pc._transceive(transceiver,
                params.codecs.length > 0,
                false)
            }
          })
        }

        pc._localDescription = {
          type: description.type,
          sdp: description.sdp
        }
        if (description.type === 'offer') {
          pc._updateSignalingState('have-local-offer')
        } else {
          pc._updateSignalingState('stable')
        }

        return Promise.resolve()
      }

      RTCPeerConnection.prototype.setRemoteDescription = function(description) {
        var pc = this

        // Note: pranswer is not supported.
        if (['offer', 'answer'].indexOf(description.type) === -1) {
          return Promise.reject(makeError('TypeError',
            'Unsupported type "' + description.type + '"'))
        }

        if (!isActionAllowedInSignalingState('setRemoteDescription',
          description.type, pc.signalingState) || pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
            'Can not set remote ' + description.type +
          ' in state ' + pc.signalingState))
        }

        var streams = {}
        pc.remoteStreams.forEach(function(stream) {
          streams[stream.id] = stream
        })
        var receiverList = []
        var sections = SDPUtils.splitSections(description.sdp)
        var sessionpart = sections.shift()
        var isIceLite = SDPUtils.matchPrefix(sessionpart,
          'a=ice-lite').length > 0
        var usingBundle = SDPUtils.matchPrefix(sessionpart,
          'a=group:BUNDLE ').length > 0
        pc.usingBundle = usingBundle
        var iceOptions = SDPUtils.matchPrefix(sessionpart,
          'a=ice-options:')[0]
        if (iceOptions) {
          pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
            .indexOf('trickle') >= 0
        } else {
          pc.canTrickleIceCandidates = false
        }

        sections.forEach(function(mediaSection, sdpMLineIndex) {
          var lines = SDPUtils.splitLines(mediaSection)
          var kind = SDPUtils.getKind(mediaSection)
          // treat bundle-only as not-rejected.
          var rejected = SDPUtils.isRejected(mediaSection) &&
          SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0
          var protocol = lines[0].substr(2).split(' ')[2]

          var direction = SDPUtils.getDirection(mediaSection, sessionpart)
          var remoteMsid = SDPUtils.parseMsid(mediaSection)

          var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier()

          // Reject datachannels which are not implemented yet.
          if (rejected || (kind === 'application' && (protocol === 'DTLS/SCTP' ||
          protocol === 'UDP/DTLS/SCTP'))) {
            // TODO: this is dangerous in the case where a non-rejected m-line
            //     becomes rejected.
            pc.transceivers[sdpMLineIndex] = {
              mid: mid,
              kind: kind,
              protocol: protocol,
              rejected: true
            }
            return
          }

          if (!rejected && pc.transceivers[sdpMLineIndex] &&
          pc.transceivers[sdpMLineIndex].rejected) {
            // recycle a rejected transceiver.
            pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true)
          }

          var transceiver
          var iceGatherer
          var iceTransport
          var dtlsTransport
          var rtpReceiver
          var sendEncodingParameters
          var recvEncodingParameters
          var localCapabilities

          var track
          // FIXME: ensure the mediaSection has rtcp-mux set.
          var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection)
          var remoteIceParameters
          var remoteDtlsParameters
          if (!rejected) {
            remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
              sessionpart)
            remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
              sessionpart)
            remoteDtlsParameters.role = 'client'
          }
          recvEncodingParameters =
          SDPUtils.parseRtpEncodingParameters(mediaSection)

          var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection)

          var isComplete = SDPUtils.matchPrefix(mediaSection,
            'a=end-of-candidates', sessionpart).length > 0
          var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
            .map(function(cand) {
              return SDPUtils.parseCandidate(cand)
            })
            .filter(function(cand) {
              return cand.component === 1
            })

          // Check if we can use BUNDLE and dispose transports.
          if ((description.type === 'offer' || description.type === 'answer') &&
          !rejected && usingBundle && sdpMLineIndex > 0 &&
          pc.transceivers[sdpMLineIndex]) {
            pc._disposeIceAndDtlsTransports(sdpMLineIndex)
            pc.transceivers[sdpMLineIndex].iceGatherer =
            pc.transceivers[0].iceGatherer
            pc.transceivers[sdpMLineIndex].iceTransport =
            pc.transceivers[0].iceTransport
            pc.transceivers[sdpMLineIndex].dtlsTransport =
            pc.transceivers[0].dtlsTransport
            if (pc.transceivers[sdpMLineIndex].rtpSender) {
              pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
                pc.transceivers[0].dtlsTransport)
            }
            if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
              pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
                pc.transceivers[0].dtlsTransport)
            }
          }
          if (description.type === 'offer' && !rejected) {
            transceiver = pc.transceivers[sdpMLineIndex] ||
            pc._createTransceiver(kind)
            transceiver.mid = mid

            if (!transceiver.iceGatherer) {
              transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                usingBundle)
            }

            if (cands.length && transceiver.iceTransport.state === 'new') {
              if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
                transceiver.iceTransport.setRemoteCandidates(cands)
              } else {
                cands.forEach(function(candidate) {
                  maybeAddCandidate(transceiver.iceTransport, candidate)
                })
              }
            }

            localCapabilities = window.RTCRtpReceiver.getCapabilities(kind)

            // filter RTX until additional stuff needed for RTX is implemented
            // in adapter.js
            if (edgeVersion < 15019) {
              localCapabilities.codecs = localCapabilities.codecs.filter(
                function(codec) {
                  return codec.name !== 'rtx'
                })
            }

            sendEncodingParameters = transceiver.sendEncodingParameters || [{
              ssrc: (2 * sdpMLineIndex + 2) * 1001
            }]

            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
            var isNewTrack = false
            if (direction === 'sendrecv' || direction === 'sendonly') {
              isNewTrack = !transceiver.rtpReceiver
              rtpReceiver = transceiver.rtpReceiver ||
              new window.RTCRtpReceiver(transceiver.dtlsTransport, kind)

              if (isNewTrack) {
                var stream
                track = rtpReceiver.track
                // FIXME: does not work with Plan B.
                if (remoteMsid && remoteMsid.stream === '-') {
                  // no-op. a stream id of '-' means: no associated stream.
                } else if (remoteMsid) {
                  if (!streams[remoteMsid.stream]) {
                    streams[remoteMsid.stream] = new window.MediaStream()
                    Object.defineProperty(streams[remoteMsid.stream], 'id', {
                      get: function() {
                        return remoteMsid.stream
                      }
                    })
                  }
                  Object.defineProperty(track, 'id', {
                    get: function() {
                      return remoteMsid.track
                    }
                  })
                  stream = streams[remoteMsid.stream]
                } else {
                  if (!streams.default) {
                    streams.default = new window.MediaStream()
                  }
                  stream = streams.default
                }
                if (stream) {
                  addTrackToStreamAndFireEvent(track, stream)
                  transceiver.associatedRemoteMediaStreams.push(stream)
                }
                receiverList.push([track, rtpReceiver, stream])
              }
            } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
              transceiver.associatedRemoteMediaStreams.forEach(function(s) {
                var nativeTrack = s.getTracks().find(function(t) {
                  return t.id === transceiver.rtpReceiver.track.id
                })
                if (nativeTrack) {
                  removeTrackFromStreamAndFireEvent(nativeTrack, s)
                }
              })
              transceiver.associatedRemoteMediaStreams = []
            }

            transceiver.localCapabilities = localCapabilities
            transceiver.remoteCapabilities = remoteCapabilities
            transceiver.rtpReceiver = rtpReceiver
            transceiver.rtcpParameters = rtcpParameters
            transceiver.sendEncodingParameters = sendEncodingParameters
            transceiver.recvEncodingParameters = recvEncodingParameters

            // Start the RTCRtpReceiver now. The RTPSender is started in
            // setLocalDescription.
            pc._transceive(pc.transceivers[sdpMLineIndex],
              false,
              isNewTrack)
          } else if (description.type === 'answer' && !rejected) {
            transceiver = pc.transceivers[sdpMLineIndex]
            iceGatherer = transceiver.iceGatherer
            iceTransport = transceiver.iceTransport
            dtlsTransport = transceiver.dtlsTransport
            rtpReceiver = transceiver.rtpReceiver
            sendEncodingParameters = transceiver.sendEncodingParameters
            localCapabilities = transceiver.localCapabilities

            pc.transceivers[sdpMLineIndex].recvEncodingParameters =
            recvEncodingParameters
            pc.transceivers[sdpMLineIndex].remoteCapabilities =
            remoteCapabilities
            pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters

            if (cands.length && iceTransport.state === 'new') {
              if ((isIceLite || isComplete) &&
              (!usingBundle || sdpMLineIndex === 0)) {
                iceTransport.setRemoteCandidates(cands)
              } else {
                cands.forEach(function(candidate) {
                  maybeAddCandidate(transceiver.iceTransport, candidate)
                })
              }
            }

            if (!usingBundle || sdpMLineIndex === 0) {
              if (iceTransport.state === 'new') {
                iceTransport.start(iceGatherer, remoteIceParameters,
                  'controlling')
              }
              if (dtlsTransport.state === 'new') {
                dtlsTransport.start(remoteDtlsParameters)
              }
            }

            // If the offer contained RTX but the answer did not,
            // remove RTX from sendEncodingParameters.
            var commonCapabilities = getCommonCapabilities(
              transceiver.localCapabilities,
              transceiver.remoteCapabilities)

            var hasRtx = commonCapabilities.codecs.filter(function(c) {
              return c.name.toLowerCase() === 'rtx'
            }).length
            if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
              delete transceiver.sendEncodingParameters[0].rtx
            }

            pc._transceive(transceiver,
              direction === 'sendrecv' || direction === 'recvonly',
              direction === 'sendrecv' || direction === 'sendonly')

            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
            if (rtpReceiver &&
            (direction === 'sendrecv' || direction === 'sendonly')) {
              track = rtpReceiver.track
              if (remoteMsid) {
                if (!streams[remoteMsid.stream]) {
                  streams[remoteMsid.stream] = new window.MediaStream()
                }
                addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream])
                receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]])
              } else {
                if (!streams.default) {
                  streams.default = new window.MediaStream()
                }
                addTrackToStreamAndFireEvent(track, streams.default)
                receiverList.push([track, rtpReceiver, streams.default])
              }
            } else {
              // FIXME: actually the receiver should be created later.
              delete transceiver.rtpReceiver
            }
          }
        })

        if (pc._dtlsRole === undefined) {
          pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive'
        }

        pc._remoteDescription = {
          type: description.type,
          sdp: description.sdp
        }
        if (description.type === 'offer') {
          pc._updateSignalingState('have-remote-offer')
        } else {
          pc._updateSignalingState('stable')
        }
        Object.keys(streams).forEach(function(sid) {
          var stream = streams[sid]
          if (stream.getTracks().length) {
            if (pc.remoteStreams.indexOf(stream) === -1) {
              pc.remoteStreams.push(stream)
              var event = new Event('addstream')
              event.stream = stream
              window.setTimeout(function() {
                pc._dispatchEvent('addstream', event)
              })
            }

            receiverList.forEach(function(item) {
              var track = item[0]
              var receiver = item[1]
              if (stream.id !== item[2].id) {
                return
              }
              fireAddTrack(pc, track, receiver, [stream])
            })
          }
        })
        receiverList.forEach(function(item) {
          if (item[2]) {
            return
          }
          fireAddTrack(pc, item[0], item[1], [])
        })

        // check whether addIceCandidate({}) was called within four seconds after
        // setRemoteDescription.
        window.setTimeout(function() {
          if (!(pc && pc.transceivers)) {
            return
          }
          pc.transceivers.forEach(function(transceiver) {
            if (transceiver.iceTransport &&
            transceiver.iceTransport.state === 'new' &&
            transceiver.iceTransport.getRemoteCandidates().length > 0) {
              console.warn('Timeout for addRemoteCandidate. Consider sending ' +
              'an end-of-candidates notification')
              transceiver.iceTransport.addRemoteCandidate({})
            }
          })
        }, 4000)

        return Promise.resolve()
      }

      RTCPeerConnection.prototype.close = function() {
        this.transceivers.forEach(function(transceiver) {
          /* not yet
      if (transceiver.iceGatherer) {
        transceiver.iceGatherer.close();
      }
      */
          if (transceiver.iceTransport) {
            transceiver.iceTransport.stop()
          }
          if (transceiver.dtlsTransport) {
            transceiver.dtlsTransport.stop()
          }
          if (transceiver.rtpSender) {
            transceiver.rtpSender.stop()
          }
          if (transceiver.rtpReceiver) {
            transceiver.rtpReceiver.stop()
          }
        })
        // FIXME: clean up tracks, local streams, remote streams, etc
        this._isClosed = true
        this._updateSignalingState('closed')
      }

      // Update the signaling state.
      RTCPeerConnection.prototype._updateSignalingState = function(newState) {
        this.signalingState = newState
        var event = new Event('signalingstatechange')
        this._dispatchEvent('signalingstatechange', event)
      }

      // Determine whether to fire the negotiationneeded event.
      RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
        var pc = this
        if (this.signalingState !== 'stable' || this.needNegotiation === true) {
          return
        }
        this.needNegotiation = true
        window.setTimeout(function() {
          if (pc.needNegotiation) {
            pc.needNegotiation = false
            var event = new Event('negotiationneeded')
            pc._dispatchEvent('negotiationneeded', event)
          }
        }, 0)
      }

      // Update the ice connection state.
      RTCPeerConnection.prototype._updateIceConnectionState = function() {
        var newState
        var states = {
          'new': 0,
          closed: 0,
          checking: 0,
          connected: 0,
          completed: 0,
          disconnected: 0,
          failed: 0
        }
        this.transceivers.forEach(function(transceiver) {
          if (transceiver.iceTransport && !transceiver.rejected) {
            states[transceiver.iceTransport.state]++
          }
        })

        newState = 'new'
        if (states.failed > 0) {
          newState = 'failed'
        } else if (states.checking > 0) {
          newState = 'checking'
        } else if (states.disconnected > 0) {
          newState = 'disconnected'
        } else if (states.new > 0) {
          newState = 'new'
        } else if (states.connected > 0) {
          newState = 'connected'
        } else if (states.completed > 0) {
          newState = 'completed'
        }

        if (newState !== this.iceConnectionState) {
          this.iceConnectionState = newState
          var event = new Event('iceconnectionstatechange')
          this._dispatchEvent('iceconnectionstatechange', event)
        }
      }

      // Update the connection state.
      RTCPeerConnection.prototype._updateConnectionState = function() {
        var newState
        var states = {
          'new': 0,
          closed: 0,
          connecting: 0,
          connected: 0,
          completed: 0,
          disconnected: 0,
          failed: 0
        }
        this.transceivers.forEach(function(transceiver) {
          if (transceiver.iceTransport && transceiver.dtlsTransport &&
          !transceiver.rejected) {
            states[transceiver.iceTransport.state]++
            states[transceiver.dtlsTransport.state]++
          }
        })
        // ICETransport.completed and connected are the same for this purpose.
        states.connected += states.completed

        newState = 'new'
        if (states.failed > 0) {
          newState = 'failed'
        } else if (states.connecting > 0) {
          newState = 'connecting'
        } else if (states.disconnected > 0) {
          newState = 'disconnected'
        } else if (states.new > 0) {
          newState = 'new'
        } else if (states.connected > 0) {
          newState = 'connected'
        }

        if (newState !== this.connectionState) {
          this.connectionState = newState
          var event = new Event('connectionstatechange')
          this._dispatchEvent('connectionstatechange', event)
        }
      }

      RTCPeerConnection.prototype.createOffer = function() {
        var pc = this

        if (pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
            'Can not call createOffer after close'))
        }

        var numAudioTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'audio'
        }).length
        var numVideoTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'video'
        }).length

        // Determine number of audio and video tracks we need to send/recv.
        var offerOptions = arguments[0]
        if (offerOptions) {
          // Reject Chrome legacy constraints.
          if (offerOptions.mandatory || offerOptions.optional) {
            throw new TypeError(
              'Legacy mandatory/optional constraints not supported.')
          }
          if (offerOptions.offerToReceiveAudio !== undefined) {
            if (offerOptions.offerToReceiveAudio === true) {
              numAudioTracks = 1
            } else if (offerOptions.offerToReceiveAudio === false) {
              numAudioTracks = 0
            } else {
              numAudioTracks = offerOptions.offerToReceiveAudio
            }
          }
          if (offerOptions.offerToReceiveVideo !== undefined) {
            if (offerOptions.offerToReceiveVideo === true) {
              numVideoTracks = 1
            } else if (offerOptions.offerToReceiveVideo === false) {
              numVideoTracks = 0
            } else {
              numVideoTracks = offerOptions.offerToReceiveVideo
            }
          }
        }

        pc.transceivers.forEach(function(transceiver) {
          if (transceiver.kind === 'audio') {
            numAudioTracks--
            if (numAudioTracks < 0) {
              transceiver.wantReceive = false
            }
          } else if (transceiver.kind === 'video') {
            numVideoTracks--
            if (numVideoTracks < 0) {
              transceiver.wantReceive = false
            }
          }
        })

        // Create M-lines for recvonly streams.
        while (numAudioTracks > 0 || numVideoTracks > 0) {
          if (numAudioTracks > 0) {
            pc._createTransceiver('audio')
            numAudioTracks--
          }
          if (numVideoTracks > 0) {
            pc._createTransceiver('video')
            numVideoTracks--
          }
        }

        var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
          pc._sdpSessionVersion++)
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          // For each track, create an ice gatherer, ice transport,
          // dtls transport, potentially rtpsender and rtpreceiver.
          var track = transceiver.track
          var kind = transceiver.kind
          var mid = transceiver.mid || SDPUtils.generateIdentifier()
          transceiver.mid = mid

          if (!transceiver.iceGatherer) {
            transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
              pc.usingBundle)
          }

          var localCapabilities = window.RTCRtpSender.getCapabilities(kind)
          // filter RTX until additional stuff needed for RTX is implemented
          // in adapter.js
          if (edgeVersion < 15019) {
            localCapabilities.codecs = localCapabilities.codecs.filter(
              function(codec) {
                return codec.name !== 'rtx'
              })
          }
          localCapabilities.codecs.forEach(function(codec) {
            // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
            // by adding level-asymmetry-allowed=1
            if (codec.name === 'H264' &&
            codec.parameters['level-asymmetry-allowed'] === undefined) {
              codec.parameters['level-asymmetry-allowed'] = '1'
            }

            // for subsequent offers, we might have to re-use the payload
            // type of the last offer.
            if (transceiver.remoteCapabilities &&
            transceiver.remoteCapabilities.codecs) {
              transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                codec.clockRate === remoteCodec.clockRate) {
                  codec.preferredPayloadType = remoteCodec.payloadType
                }
              })
            }
          })
          localCapabilities.headerExtensions.forEach(function(hdrExt) {
            var remoteExtensions = transceiver.remoteCapabilities &&
            transceiver.remoteCapabilities.headerExtensions || []
            remoteExtensions.forEach(function(rHdrExt) {
              if (hdrExt.uri === rHdrExt.uri) {
                hdrExt.id = rHdrExt.id
              }
            })
          })

          // generate an ssrc now, to be used later in rtpSender.send
          var sendEncodingParameters = transceiver.sendEncodingParameters || [{
            ssrc: (2 * sdpMLineIndex + 1) * 1001
          }]
          if (track) {
            // add RTX
            if (edgeVersion >= 15019 && kind === 'video' &&
            !sendEncodingParameters[0].rtx) {
              sendEncodingParameters[0].rtx = {
                ssrc: sendEncodingParameters[0].ssrc + 1
              }
            }
          }

          if (transceiver.wantReceive) {
            transceiver.rtpReceiver = new window.RTCRtpReceiver(
              transceiver.dtlsTransport, kind)
          }

          transceiver.localCapabilities = localCapabilities
          transceiver.sendEncodingParameters = sendEncodingParameters
        })

        // always offer BUNDLE and dispose on return if not supported.
        if (pc._config.bundlePolicy !== 'max-compat') {
          sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
            return t.mid
          }).join(' ') + '\r\n'
        }
        sdp += 'a=ice-options:trickle\r\n'

        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
            'offer', transceiver.stream, pc._dtlsRole)
          sdp += 'a=rtcp-rsize\r\n'

          if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
          (sdpMLineIndex === 0 || !pc.usingBundle)) {
            transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
              cand.component = 1
              sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n'
            })

            if (transceiver.iceGatherer.state === 'completed') {
              sdp += 'a=end-of-candidates\r\n'
            }
          }
        })

        var desc = new window.RTCSessionDescription({
          type: 'offer',
          sdp: sdp
        })
        return Promise.resolve(desc)
      }

      RTCPeerConnection.prototype.createAnswer = function() {
        var pc = this

        if (pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
            'Can not call createAnswer after close'))
        }

        if (!(pc.signalingState === 'have-remote-offer' ||
        pc.signalingState === 'have-local-pranswer')) {
          return Promise.reject(makeError('InvalidStateError',
            'Can not call createAnswer in signalingState ' + pc.signalingState))
        }

        var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
          pc._sdpSessionVersion++)
        if (pc.usingBundle) {
          sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
            return t.mid
          }).join(' ') + '\r\n'
        }
        sdp += 'a=ice-options:trickle\r\n'

        var mediaSectionsInOffer = SDPUtils.getMediaSections(
          pc._remoteDescription.sdp).length
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
            return
          }
          if (transceiver.rejected) {
            if (transceiver.kind === 'application') {
              if (transceiver.protocol === 'DTLS/SCTP') { // legacy fmt
                sdp += 'm=application 0 DTLS/SCTP 5000\r\n'
              } else {
                sdp += 'm=application 0 ' + transceiver.protocol +
                ' webrtc-datachannel\r\n'
              }
            } else if (transceiver.kind === 'audio') {
              sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
              'a=rtpmap:0 PCMU/8000\r\n'
            } else if (transceiver.kind === 'video') {
              sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
              'a=rtpmap:120 VP8/90000\r\n'
            }
            sdp += 'c=IN IP4 0.0.0.0\r\n' +
            'a=inactive\r\n' +
            'a=mid:' + transceiver.mid + '\r\n'
            return
          }

          // FIXME: look at direction.
          if (transceiver.stream) {
            var localTrack
            if (transceiver.kind === 'audio') {
              localTrack = transceiver.stream.getAudioTracks()[0]
            } else if (transceiver.kind === 'video') {
              localTrack = transceiver.stream.getVideoTracks()[0]
            }
            if (localTrack) {
              // add RTX
              if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
              !transceiver.sendEncodingParameters[0].rtx) {
                transceiver.sendEncodingParameters[0].rtx = {
                  ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
                }
              }
            }
          }

          // Calculate intersection of capabilities.
          var commonCapabilities = getCommonCapabilities(
            transceiver.localCapabilities,
            transceiver.remoteCapabilities)

          var hasRtx = commonCapabilities.codecs.filter(function(c) {
            return c.name.toLowerCase() === 'rtx'
          }).length
          if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
            delete transceiver.sendEncodingParameters[0].rtx
          }

          sdp += writeMediaSection(transceiver, commonCapabilities,
            'answer', transceiver.stream, pc._dtlsRole)
          if (transceiver.rtcpParameters &&
          transceiver.rtcpParameters.reducedSize) {
            sdp += 'a=rtcp-rsize\r\n'
          }
        })

        var desc = new window.RTCSessionDescription({
          type: 'answer',
          sdp: sdp
        })
        return Promise.resolve(desc)
      }

      RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
        var pc = this
        var sections
        if (candidate && !(candidate.sdpMLineIndex !== undefined ||
        candidate.sdpMid)) {
          return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'))
        }

        // TODO: needs to go into ops queue.
        return new Promise(function(resolve, reject) {
          if (!pc._remoteDescription) {
            return reject(makeError('InvalidStateError',
              'Can not add ICE candidate without a remote description'))
          } else if (!candidate || candidate.candidate === '') {
            for (var j = 0; j < pc.transceivers.length; j++) {
              if (pc.transceivers[j].rejected) {
                continue
              }
              pc.transceivers[j].iceTransport.addRemoteCandidate({})
              sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp)
              sections[j] += 'a=end-of-candidates\r\n'
              pc._remoteDescription.sdp =
              SDPUtils.getDescription(pc._remoteDescription.sdp) +
              sections.join('')
              if (pc.usingBundle) {
                break
              }
            }
          } else {
            var sdpMLineIndex = candidate.sdpMLineIndex
            if (candidate.sdpMid) {
              for (var i = 0; i < pc.transceivers.length; i++) {
                if (pc.transceivers[i].mid === candidate.sdpMid) {
                  sdpMLineIndex = i
                  break
                }
              }
            }
            var transceiver = pc.transceivers[sdpMLineIndex]
            if (transceiver) {
              if (transceiver.rejected) {
                return resolve()
              }
              var cand = Object.keys(candidate.candidate).length > 0
                ? SDPUtils.parseCandidate(candidate.candidate) : {}
              // Ignore Chrome's invalid candidates since Edge does not like them.
              if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
                return resolve()
              }
              // Ignore RTCP candidates, we assume RTCP-MUX.
              if (cand.component && cand.component !== 1) {
                return resolve()
              }
              // when using bundle, avoid adding candidates to the wrong
              // ice transport. And avoid adding candidates added in the SDP.
              if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
              transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
                if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
                  return reject(makeError('OperationError',
                    'Can not add ICE candidate'))
                }
              }

              // update the remoteDescription.
              var candidateString = candidate.candidate.trim()
              if (candidateString.indexOf('a=') === 0) {
                candidateString = candidateString.substr(2)
              }
              sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp)
              sections[sdpMLineIndex] += 'a=' +
              (cand.type ? candidateString : 'end-of-candidates') +
              '\r\n'
              pc._remoteDescription.sdp =
              SDPUtils.getDescription(pc._remoteDescription.sdp) +
              sections.join('')
            } else {
              return reject(makeError('OperationError',
                'Can not add ICE candidate'))
            }
          }
          resolve()
        })
      }

      RTCPeerConnection.prototype.getStats = function(selector) {
        if (selector && selector instanceof window.MediaStreamTrack) {
          var senderOrReceiver = null
          this.transceivers.forEach(function(transceiver) {
            if (transceiver.rtpSender &&
            transceiver.rtpSender.track === selector) {
              senderOrReceiver = transceiver.rtpSender
            } else if (transceiver.rtpReceiver &&
            transceiver.rtpReceiver.track === selector) {
              senderOrReceiver = transceiver.rtpReceiver
            }
          })
          if (!senderOrReceiver) {
            throw makeError('InvalidAccessError', 'Invalid selector.')
          }
          return senderOrReceiver.getStats()
        }

        var promises = []
        this.transceivers.forEach(function(transceiver) {
          ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
            'dtlsTransport'].forEach(function(method) {
            if (transceiver[method]) {
              promises.push(transceiver[method].getStats())
            }
          })
        })
        return Promise.all(promises).then(function(allStats) {
          var results = new Map()
          allStats.forEach(function(stats) {
            stats.forEach(function(stat) {
              results.set(stat.id, stat)
            })
          })
          return results
        })
      }

      // fix low-level stat names and return Map instead of object.
      var ortcObjects = ['RTCRtpSender', 'RTCRtpReceiver', 'RTCIceGatherer',
        'RTCIceTransport', 'RTCDtlsTransport']
      ortcObjects.forEach(function(ortcObjectName) {
        var obj = window[ortcObjectName]
        if (obj && obj.prototype && obj.prototype.getStats) {
          var nativeGetstats = obj.prototype.getStats
          obj.prototype.getStats = function() {
            return nativeGetstats.apply(this)
              .then(function(nativeStats) {
                var mapStats = new Map()
                Object.keys(nativeStats).forEach(function(id) {
                  nativeStats[id].type = fixStatsType(nativeStats[id])
                  mapStats.set(id, nativeStats[id])
                })
                return mapStats
              })
          }
        }
      })

      // legacy callback shims. Should be moved to adapter.js some days.
      var methods = ['createOffer', 'createAnswer']
      methods.forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method]
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments
          if (typeof args[0] === 'function' ||
          typeof args[1] === 'function') { // legacy
            return nativeMethod.apply(this, [arguments[2]])
              .then(function(description) {
                if (typeof args[0] === 'function') {
                  args[0].apply(null, [description])
                }
              }, function(error) {
                if (typeof args[1] === 'function') {
                  args[1].apply(null, [error])
                }
              })
          }
          return nativeMethod.apply(this, arguments)
        }
      })

      methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
      methods.forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method]
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments
          if (typeof args[1] === 'function' ||
          typeof args[2] === 'function') { // legacy
            return nativeMethod.apply(this, arguments)
              .then(function() {
                if (typeof args[1] === 'function') {
                  args[1].apply(null)
                }
              }, function(error) {
                if (typeof args[2] === 'function') {
                  args[2].apply(null, [error])
                }
              })
          }
          return nativeMethod.apply(this, arguments)
        }
      });

      // getStats is special. It doesn't have a spec legacy method yet we support
      // getStats(something, cb) without error callbacks.
      ['getStats'].forEach(function(method) {
        var nativeMethod = RTCPeerConnection.prototype[method]
        RTCPeerConnection.prototype[method] = function() {
          var args = arguments
          if (typeof args[1] === 'function') {
            return nativeMethod.apply(this, arguments)
              .then(function() {
                if (typeof args[1] === 'function') {
                  args[1].apply(null)
                }
              })
          }
          return nativeMethod.apply(this, arguments)
        }
      })

      return RTCPeerConnection
    }
  }, { 'sdp': 17 }], 17: [function(require, module, exports) {
    /* eslint-env node */
    'use strict'

    // SDP helpers.
    var SDPUtils = {}

    // Generate an alphanumeric identifier for cname or mids.
    // TODO: use UUIDs instead? https://gist.github.com/jed/982883
    SDPUtils.generateIdentifier = function() {
      return Math.random().toString(36).substr(2, 10)
    }

    // The RTCP CNAME used by all peerconnections from the same JS.
    SDPUtils.localCName = SDPUtils.generateIdentifier()

    // Splits SDP into lines, dealing with both CRLF and LF.
    SDPUtils.splitLines = function(blob) {
      return blob.trim().split('\n').map(function(line) {
        return line.trim()
      })
    }
    // Splits SDP into sessionpart and mediasections. Ensures CRLF.
    SDPUtils.splitSections = function(blob) {
      var parts = blob.split('\nm=')
      return parts.map(function(part, index) {
        return (index > 0 ? 'm=' + part : part).trim() + '\r\n'
      })
    }

    // returns the session description.
    SDPUtils.getDescription = function(blob) {
      var sections = SDPUtils.splitSections(blob)
      return sections && sections[0]
    }

    // returns the individual media sections.
    SDPUtils.getMediaSections = function(blob) {
      var sections = SDPUtils.splitSections(blob)
      sections.shift()
      return sections
    }

    // Returns lines that start with a certain prefix.
    SDPUtils.matchPrefix = function(blob, prefix) {
      return SDPUtils.splitLines(blob).filter(function(line) {
        return line.indexOf(prefix) === 0
      })
    }

    // Parses an ICE candidate line. Sample input:
    // candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
    // rport 55996"
    SDPUtils.parseCandidate = function(line) {
      var parts
      // Parse both variants.
      if (line.indexOf('a=candidate:') === 0) {
        parts = line.substring(12).split(' ')
      } else {
        parts = line.substring(10).split(' ')
      }

      var candidate = {
        foundation: parts[0],
        component: parseInt(parts[1], 10),
        protocol: parts[2].toLowerCase(),
        priority: parseInt(parts[3], 10),
        ip: parts[4],
        address: parts[4], // address is an alias for ip.
        port: parseInt(parts[5], 10),
        // skip parts[6] == 'typ'
        type: parts[7]
      }

      for (var i = 8; i < parts.length; i += 2) {
        switch (parts[i]) {
          case 'raddr':
            candidate.relatedAddress = parts[i + 1]
            break
          case 'rport':
            candidate.relatedPort = parseInt(parts[i + 1], 10)
            break
          case 'tcptype':
            candidate.tcpType = parts[i + 1]
            break
          case 'ufrag':
            candidate.ufrag = parts[i + 1] // for backward compability.
            candidate.usernameFragment = parts[i + 1]
            break
          default: // extension handling, in particular ufrag
            candidate[parts[i]] = parts[i + 1]
            break
        }
      }
      return candidate
    }

    // Translates a candidate object into SDP candidate attribute.
    SDPUtils.writeCandidate = function(candidate) {
      var sdp = []
      sdp.push(candidate.foundation)
      sdp.push(candidate.component)
      sdp.push(candidate.protocol.toUpperCase())
      sdp.push(candidate.priority)
      sdp.push(candidate.address || candidate.ip)
      sdp.push(candidate.port)

      var type = candidate.type
      sdp.push('typ')
      sdp.push(type)
      if (type !== 'host' && candidate.relatedAddress &&
      candidate.relatedPort) {
        sdp.push('raddr')
        sdp.push(candidate.relatedAddress)
        sdp.push('rport')
        sdp.push(candidate.relatedPort)
      }
      if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
        sdp.push('tcptype')
        sdp.push(candidate.tcpType)
      }
      if (candidate.usernameFragment || candidate.ufrag) {
        sdp.push('ufrag')
        sdp.push(candidate.usernameFragment || candidate.ufrag)
      }
      return 'candidate:' + sdp.join(' ')
    }

    // Parses an ice-options line, returns an array of option tags.
    // a=ice-options:foo bar
    SDPUtils.parseIceOptions = function(line) {
      return line.substr(14).split(' ')
    }

    // Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
    // a=rtpmap:111 opus/48000/2
    SDPUtils.parseRtpMap = function(line) {
      var parts = line.substr(9).split(' ')
      var parsed = {
        payloadType: parseInt(parts.shift(), 10) // was: id
      }

      parts = parts[0].split('/')

      parsed.name = parts[0]
      parsed.clockRate = parseInt(parts[1], 10) // was: clockrate
      parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1
      // legacy alias, got renamed back to channels in ORTC.
      parsed.numChannels = parsed.channels
      return parsed
    }

    // Generate an a=rtpmap line from RTCRtpCodecCapability or
    // RTCRtpCodecParameters.
    SDPUtils.writeRtpMap = function(codec) {
      var pt = codec.payloadType
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType
      }
      var channels = codec.channels || codec.numChannels || 1
      return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
      (channels !== 1 ? '/' + channels : '') + '\r\n'
    }

    // Parses an a=extmap line (headerextension from RFC 5285). Sample input:
    // a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
    // a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
    SDPUtils.parseExtmap = function(line) {
      var parts = line.substr(9).split(' ')
      return {
        id: parseInt(parts[0], 10),
        direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
        uri: parts[1]
      }
    }

    // Generates a=extmap line from RTCRtpHeaderExtensionParameters or
    // RTCRtpHeaderExtension.
    SDPUtils.writeExtmap = function(headerExtension) {
      return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
        ? '/' + headerExtension.direction
        : '') +
      ' ' + headerExtension.uri + '\r\n'
    }

    // Parses an ftmp line, returns dictionary. Sample input:
    // a=fmtp:96 vbr=on;cng=on
    // Also deals with vbr=on; cng=on
    SDPUtils.parseFmtp = function(line) {
      var parsed = {}
      var kv
      var parts = line.substr(line.indexOf(' ') + 1).split(';')
      for (var j = 0; j < parts.length; j++) {
        kv = parts[j].trim().split('=')
        parsed[kv[0].trim()] = kv[1]
      }
      return parsed
    }

    // Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeFmtp = function(codec) {
      var line = ''
      var pt = codec.payloadType
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType
      }
      if (codec.parameters && Object.keys(codec.parameters).length) {
        var params = []
        Object.keys(codec.parameters).forEach(function(param) {
          if (codec.parameters[param]) {
            params.push(param + '=' + codec.parameters[param])
          } else {
            params.push(param)
          }
        })
        line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n'
      }
      return line
    }

    // Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
    // a=rtcp-fb:98 nack rpsi
    SDPUtils.parseRtcpFb = function(line) {
      var parts = line.substr(line.indexOf(' ') + 1).split(' ')
      return {
        type: parts.shift(),
        parameter: parts.join(' ')
      }
    }
    // Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeRtcpFb = function(codec) {
      var lines = ''
      var pt = codec.payloadType
      if (codec.preferredPayloadType !== undefined) {
        pt = codec.preferredPayloadType
      }
      if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
        // FIXME: special handling for trr-int?
        codec.rtcpFeedback.forEach(function(fb) {
          lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
          '\r\n'
        })
      }
      return lines
    }

    // Parses an RFC 5576 ssrc media attribute. Sample input:
    // a=ssrc:3735928559 cname:something
    SDPUtils.parseSsrcMedia = function(line) {
      var sp = line.indexOf(' ')
      var parts = {
        ssrc: parseInt(line.substr(7, sp - 7), 10)
      }
      var colon = line.indexOf(':', sp)
      if (colon > -1) {
        parts.attribute = line.substr(sp + 1, colon - sp - 1)
        parts.value = line.substr(colon + 1)
      } else {
        parts.attribute = line.substr(sp + 1)
      }
      return parts
    }

    SDPUtils.parseSsrcGroup = function(line) {
      var parts = line.substr(13).split(' ')
      return {
        semantics: parts.shift(),
        ssrcs: parts.map(function(ssrc) {
          return parseInt(ssrc, 10)
        })
      }
    }

    // Extracts the MID (RFC 5888) from a media section.
    // returns the MID or undefined if no mid line was found.
    SDPUtils.getMid = function(mediaSection) {
      var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0]
      if (mid) {
        return mid.substr(6)
      }
    }

    SDPUtils.parseFingerprint = function(line) {
      var parts = line.substr(14).split(' ')
      return {
        algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
        value: parts[1]
      }
    }

    // Extracts DTLS parameters from SDP media section or sessionpart.
    // FIXME: for consistency with other functions this should only
    //   get the fingerprint line as input. See also getIceParameters.
    SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
      var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=fingerprint:')
      // Note: a=setup line is ignored since we use the 'auto' role.
      // Note2: 'algorithm' is not case sensitive except in Edge.
      return {
        role: 'auto',
        fingerprints: lines.map(SDPUtils.parseFingerprint)
      }
    }

    // Serializes DTLS parameters to SDP.
    SDPUtils.writeDtlsParameters = function(params, setupType) {
      var sdp = 'a=setup:' + setupType + '\r\n'
      params.fingerprints.forEach(function(fp) {
        sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n'
      })
      return sdp
    }

    // Parses a=crypto lines into
    //   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
    SDPUtils.parseCryptoLine = function(line) {
      var parts = line.substr(9).split(' ')
      return {
        tag: parseInt(parts[0], 10),
        cryptoSuite: parts[1],
        keyParams: parts[2],
        sessionParams: parts.slice(3)
      }
    }

    SDPUtils.writeCryptoLine = function(parameters) {
      return 'a=crypto:' + parameters.tag + ' ' +
    parameters.cryptoSuite + ' ' +
    (typeof parameters.keyParams === 'object'
      ? SDPUtils.writeCryptoKeyParams(parameters.keyParams)
      : parameters.keyParams) +
    (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') +
    '\r\n'
    }

    // Parses the crypto key parameters into
    //   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
    SDPUtils.parseCryptoKeyParams = function(keyParams) {
      if (keyParams.indexOf('inline:') !== 0) {
        return null
      }
      var parts = keyParams.substr(7).split('|')
      return {
        keyMethod: 'inline',
        keySalt: parts[0],
        lifeTime: parts[1],
        mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
        mkiLength: parts[2] ? parts[2].split(':')[1] : undefined
      }
    }

    SDPUtils.writeCryptoKeyParams = function(keyParams) {
      return keyParams.keyMethod + ':' +
    keyParams.keySalt +
    (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') +
    (keyParams.mkiValue && keyParams.mkiLength
      ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength
      : '')
    }

    // Extracts all SDES paramters.
    SDPUtils.getCryptoParameters = function(mediaSection, sessionpart) {
      var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=crypto:')
      return lines.map(SDPUtils.parseCryptoLine)
    }

    // Parses ICE information from SDP media section or sessionpart.
    // FIXME: for consistency with other functions this should only
    //   get the ice-ufrag and ice-pwd lines as input.
    SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
      var ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=ice-ufrag:')[0]
      var pwd = SDPUtils.matchPrefix(mediaSection + sessionpart,
        'a=ice-pwd:')[0]
      if (!(ufrag && pwd)) {
        return null
      }
      return {
        usernameFragment: ufrag.substr(12),
        password: pwd.substr(10)
      }
    }

    // Serializes ICE parameters to SDP.
    SDPUtils.writeIceParameters = function(params) {
      return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
      'a=ice-pwd:' + params.password + '\r\n'
    }

    // Parses the SDP media section and returns RTCRtpParameters.
    SDPUtils.parseRtpParameters = function(mediaSection) {
      var description = {
        codecs: [],
        headerExtensions: [],
        fecMechanisms: [],
        rtcp: []
      }
      var lines = SDPUtils.splitLines(mediaSection)
      var mline = lines[0].split(' ')
      for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
        var pt = mline[i]
        var rtpmapline = SDPUtils.matchPrefix(
          mediaSection, 'a=rtpmap:' + pt + ' ')[0]
        if (rtpmapline) {
          var codec = SDPUtils.parseRtpMap(rtpmapline)
          var fmtps = SDPUtils.matchPrefix(
            mediaSection, 'a=fmtp:' + pt + ' ')
          // Only the first a=fmtp:<pt> is considered.
          codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {}
          codec.rtcpFeedback = SDPUtils.matchPrefix(
            mediaSection, 'a=rtcp-fb:' + pt + ' ')
            .map(SDPUtils.parseRtcpFb)
          description.codecs.push(codec)
          // parse FEC mechanisms from rtpmap lines.
          switch (codec.name.toUpperCase()) {
            case 'RED':
            case 'ULPFEC':
              description.fecMechanisms.push(codec.name.toUpperCase())
              break
            default: // only RED and ULPFEC are recognized as FEC mechanisms.
              break
          }
        }
      }
      SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
        description.headerExtensions.push(SDPUtils.parseExtmap(line))
      })
      // FIXME: parse rtcp.
      return description
    }

    // Generates parts of the SDP media section describing the capabilities /
    // parameters.
    SDPUtils.writeRtpDescription = function(kind, caps) {
      var sdp = ''

      // Build the mline.
      sdp += 'm=' + kind + ' '
      sdp += caps.codecs.length > 0 ? '9' : '0' // reject if no codecs.
      sdp += ' UDP/TLS/RTP/SAVPF '
      sdp += caps.codecs.map(function(codec) {
        if (codec.preferredPayloadType !== undefined) {
          return codec.preferredPayloadType
        }
        return codec.payloadType
      }).join(' ') + '\r\n'

      sdp += 'c=IN IP4 0.0.0.0\r\n'
      sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n'

      // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
      caps.codecs.forEach(function(codec) {
        sdp += SDPUtils.writeRtpMap(codec)
        sdp += SDPUtils.writeFmtp(codec)
        sdp += SDPUtils.writeRtcpFb(codec)
      })
      var maxptime = 0
      caps.codecs.forEach(function(codec) {
        if (codec.maxptime > maxptime) {
          maxptime = codec.maxptime
        }
      })
      if (maxptime > 0) {
        sdp += 'a=maxptime:' + maxptime + '\r\n'
      }
      sdp += 'a=rtcp-mux\r\n'

      if (caps.headerExtensions) {
        caps.headerExtensions.forEach(function(extension) {
          sdp += SDPUtils.writeExtmap(extension)
        })
      }
      // FIXME: write fecMechanisms.
      return sdp
    }

    // Parses the SDP media section and returns an array of
    // RTCRtpEncodingParameters.
    SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
      var encodingParameters = []
      var description = SDPUtils.parseRtpParameters(mediaSection)
      var hasRed = description.fecMechanisms.indexOf('RED') !== -1
      var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1

      // filter a=ssrc:... cname:, ignore PlanB-msid
      var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line)
        })
        .filter(function(parts) {
          return parts.attribute === 'cname'
        })
      var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc
      var secondarySsrc

      var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
        .map(function(line) {
          var parts = line.substr(17).split(' ')
          return parts.map(function(part) {
            return parseInt(part, 10)
          })
        })
      if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
        secondarySsrc = flows[0][1]
      }

      description.codecs.forEach(function(codec) {
        if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
          var encParam = {
            ssrc: primarySsrc,
            codecPayloadType: parseInt(codec.parameters.apt, 10)
          }
          if (primarySsrc && secondarySsrc) {
            encParam.rtx = { ssrc: secondarySsrc }
          }
          encodingParameters.push(encParam)
          if (hasRed) {
            encParam = JSON.parse(JSON.stringify(encParam))
            encParam.fec = {
              ssrc: primarySsrc,
              mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
            }
            encodingParameters.push(encParam)
          }
        }
      })
      if (encodingParameters.length === 0 && primarySsrc) {
        encodingParameters.push({
          ssrc: primarySsrc
        })
      }

      // we support both b=AS and b=TIAS but interpret AS as TIAS.
      var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=')
      if (bandwidth.length) {
        if (bandwidth[0].indexOf('b=TIAS:') === 0) {
          bandwidth = parseInt(bandwidth[0].substr(7), 10)
        } else if (bandwidth[0].indexOf('b=AS:') === 0) {
          // use formula from JSEP to convert b=AS to TIAS value.
          bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95 -
          (50 * 40 * 8)
        } else {
          bandwidth = undefined
        }
        encodingParameters.forEach(function(params) {
          params.maxBitrate = bandwidth
        })
      }
      return encodingParameters
    }

    // parses http://draft.ortc.org/#rtcrtcpparameters*
    SDPUtils.parseRtcpParameters = function(mediaSection) {
      var rtcpParameters = {}

      // Gets the first SSRC. Note tha with RTX there might be multiple
      // SSRCs.
      var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line)
        })
        .filter(function(obj) {
          return obj.attribute === 'cname'
        })[0]
      if (remoteSsrc) {
        rtcpParameters.cname = remoteSsrc.value
        rtcpParameters.ssrc = remoteSsrc.ssrc
      }

      // Edge uses the compound attribute instead of reducedSize
      // compound is !reducedSize
      var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize')
      rtcpParameters.reducedSize = rsize.length > 0
      rtcpParameters.compound = rsize.length === 0

      // parses the rtcp-mux attrіbute.
      // Note that Edge does not support unmuxed RTCP.
      var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux')
      rtcpParameters.mux = mux.length > 0

      return rtcpParameters
    }

    // parses either a=msid: or a=ssrc:... msid lines and returns
    // the id of the MediaStream and MediaStreamTrack.
    SDPUtils.parseMsid = function(mediaSection) {
      var parts
      var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:')
      if (spec.length === 1) {
        parts = spec[0].substr(7).split(' ')
        return { stream: parts[0], track: parts[1] }
      }
      var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
        .map(function(line) {
          return SDPUtils.parseSsrcMedia(line)
        })
        .filter(function(msidParts) {
          return msidParts.attribute === 'msid'
        })
      if (planB.length > 0) {
        parts = planB[0].value.split(' ')
        return { stream: parts[0], track: parts[1] }
      }
    }

    // SCTP
    // parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
    // to draft-ietf-mmusic-sctp-sdp-05
    SDPUtils.parseSctpDescription = function(mediaSection) {
      var mline = SDPUtils.parseMLine(mediaSection)
      var maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:')
      var maxMessageSize
      if (maxSizeLine.length > 0) {
        maxMessageSize = parseInt(maxSizeLine[0].substr(19), 10)
      }
      if (isNaN(maxMessageSize)) {
        maxMessageSize = 65536
      }
      var sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:')
      if (sctpPort.length > 0) {
        return {
          port: parseInt(sctpPort[0].substr(12), 10),
          protocol: mline.fmt,
          maxMessageSize: maxMessageSize
        }
      }
      var sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:')
      if (sctpMapLines.length > 0) {
        var parts = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:')[0]
          .substr(10)
          .split(' ')
        return {
          port: parseInt(parts[0], 10),
          protocol: parts[1],
          maxMessageSize: maxMessageSize
        }
      }
    }

    // SCTP
    // outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
    // support by now receiving in this format, unless we originally parsed
    // as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
    // protocol of DTLS/SCTP -- without UDP/ or TCP/)
    SDPUtils.writeSctpDescription = function(media, sctp) {
      var output = []
      if (media.protocol !== 'DTLS/SCTP') {
        output = [
          'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n',
          'c=IN IP4 0.0.0.0\r\n',
          'a=sctp-port:' + sctp.port + '\r\n'
        ]
      } else {
        output = [
          'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n',
          'c=IN IP4 0.0.0.0\r\n',
          'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n'
        ]
      }
      if (sctp.maxMessageSize !== undefined) {
        output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n')
      }
      return output.join('')
    }

    // Generate a session ID for SDP.
    // https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
    // recommends using a cryptographically random +ve 64-bit value
    // but right now this should be acceptable and within the right range
    SDPUtils.generateSessionId = function() {
      return Math.random().toString().substr(2, 21)
    }

    // Write boilder plate for start of SDP
    // sessId argument is optional - if not supplied it will
    // be generated randomly
    // sessVersion is optional and defaults to 2
    // sessUser is optional and defaults to 'thisisadapterortc'
    SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
      var sessionId
      var version = sessVer !== undefined ? sessVer : 2
      if (sessId) {
        sessionId = sessId
      } else {
        sessionId = SDPUtils.generateSessionId()
      }
      var user = sessUser || 'thisisadapterortc'
      // FIXME: sess-id should be an NTP timestamp.
      return 'v=0\r\n' +
      'o=' + user + ' ' + sessionId + ' ' + version +
        ' IN IP4 127.0.0.1\r\n' +
      's=-\r\n' +
      't=0 0\r\n'
    }

    SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
      var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps)

      // Map ICE parameters (ufrag, pwd) to SDP.
      sdp += SDPUtils.writeIceParameters(
        transceiver.iceGatherer.getLocalParameters())

      // Map DTLS parameters to SDP.
      sdp += SDPUtils.writeDtlsParameters(
        transceiver.dtlsTransport.getLocalParameters(),
        type === 'offer' ? 'actpass' : 'active')

      sdp += 'a=mid:' + transceiver.mid + '\r\n'

      if (transceiver.direction) {
        sdp += 'a=' + transceiver.direction + '\r\n'
      } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
        sdp += 'a=sendrecv\r\n'
      } else if (transceiver.rtpSender) {
        sdp += 'a=sendonly\r\n'
      } else if (transceiver.rtpReceiver) {
        sdp += 'a=recvonly\r\n'
      } else {
        sdp += 'a=inactive\r\n'
      }

      if (transceiver.rtpSender) {
        // spec.
        var msid = 'msid:' + stream.id + ' ' +
        transceiver.rtpSender.track.id + '\r\n'
        sdp += 'a=' + msid

        // for Chrome.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
        ' ' + msid
        if (transceiver.sendEncodingParameters[0].rtx) {
          sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
          ' ' + msid
          sdp += 'a=ssrc-group:FID ' +
          transceiver.sendEncodingParameters[0].ssrc + ' ' +
          transceiver.sendEncodingParameters[0].rtx.ssrc +
          '\r\n'
        }
      }
      // FIXME: this should be written by writeRtpDescription.
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
      ' cname:' + SDPUtils.localCName + '\r\n'
      if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
        ' cname:' + SDPUtils.localCName + '\r\n'
      }
      return sdp
    }

    // Gets the direction from the mediaSection or the sessionpart.
    SDPUtils.getDirection = function(mediaSection, sessionpart) {
      // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
      var lines = SDPUtils.splitLines(mediaSection)
      for (var i = 0; i < lines.length; i++) {
        switch (lines[i]) {
          case 'a=sendrecv':
          case 'a=sendonly':
          case 'a=recvonly':
          case 'a=inactive':
            return lines[i].substr(2)
          default:
        // FIXME: What should happen here?
        }
      }
      if (sessionpart) {
        return SDPUtils.getDirection(sessionpart)
      }
      return 'sendrecv'
    }

    SDPUtils.getKind = function(mediaSection) {
      var lines = SDPUtils.splitLines(mediaSection)
      var mline = lines[0].split(' ')
      return mline[0].substr(2)
    }

    SDPUtils.isRejected = function(mediaSection) {
      return mediaSection.split(' ', 2)[1] === '0'
    }

    SDPUtils.parseMLine = function(mediaSection) {
      var lines = SDPUtils.splitLines(mediaSection)
      var parts = lines[0].substr(2).split(' ')
      return {
        kind: parts[0],
        port: parseInt(parts[1], 10),
        protocol: parts[2],
        fmt: parts.slice(3).join(' ')
      }
    }

    SDPUtils.parseOLine = function(mediaSection) {
      var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0]
      var parts = line.substr(2).split(' ')
      return {
        username: parts[0],
        sessionId: parts[1],
        sessionVersion: parseInt(parts[2], 10),
        netType: parts[3],
        addressType: parts[4],
        address: parts[5]
      }
    }

    // a very naive interpretation of a valid SDP.
    SDPUtils.isValidSDP = function(blob) {
      if (typeof blob !== 'string' || blob.length === 0) {
        return false
      }
      var lines = SDPUtils.splitLines(blob)
      for (var i = 0; i < lines.length; i++) {
        if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
          return false
        }
        // TODO: check the modifier a bit more.
      }
      return true
    }

    // Expose public methods.
    if (typeof module === 'object') {
      module.exports = SDPUtils
    }
  }, {}] }, {}, [1])(1)
})
